diff --git a/src/main/java/com/redislabs/university/RU102J/api/SiteStats.java b/src/main/java/com/redislabs/university/RU102J/api/SiteStats.java
index 9cddfbd..d729556 100644
--- a/src/main/java/com/redislabs/university/RU102J/api/SiteStats.java
+++ b/src/main/java/com/redislabs/university/RU102J/api/SiteStats.java
@@ -12,6 +12,7 @@ public class SiteStats {
     private Double minWhGenerated;
     private Double maxCapacity;
 
+
     /* These field names will be used by multiple classes, so we define
        them here to abide by DRY (don't repeat yourself). */
     public final static String reportingTimeField = "lastReportingTime";
diff --git a/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java b/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
index 1da030f..98b4c16 100644
--- a/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
+++ b/src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
@@ -3,88 +3,98 @@
 import com.redislabs.university.RU102J.api.MeterReading;
 import com.redislabs.university.RU102J.api.SiteStats;
 import com.redislabs.university.RU102J.script.CompareAndUpdateScript;
-import redis.clients.jedis.Jedis;
-import redis.clients.jedis.JedisPool;
-import redis.clients.jedis.Transaction;
 
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
 import java.util.Map;
 
+import redis.clients.jedis.Jedis;
+import redis.clients.jedis.JedisPool;
+import redis.clients.jedis.Transaction;
+
 public class SiteStatsDaoRedisImpl implements SiteStatsDao {
 
-    private final int weekSeconds = 60 * 60 * 24 * 7;
-    private final JedisPool jedisPool;
-    private final CompareAndUpdateScript compareAndUpdateScript;
-
-    public SiteStatsDaoRedisImpl(JedisPool jedisPool) {
-        this.jedisPool = jedisPool;
-        this.compareAndUpdateScript = new CompareAndUpdateScript(jedisPool);
-    }
-
-    // Returns the site stats for the current day
-    @Override
-    public SiteStats findById(long siteId) {
-        return findById(siteId, ZonedDateTime.now());
-    }
-
-    @Override
-    public SiteStats findById(long siteId, ZonedDateTime day) {
-        try (Jedis jedis = jedisPool.getResource()) {
-            String key = RedisSchema.getSiteStatsKey(siteId, day);
-            Map<String, String> fields = jedis.hgetAll(key);
-            if (fields == null || fields.isEmpty()) {
-                return null;
-            }
-            return new SiteStats(fields);
-        }
-    }
-
-    @Override
-    public void update(MeterReading reading) {
-        try (Jedis jedis = jedisPool.getResource()) {
-            Long siteId = reading.getSiteId();
-            ZonedDateTime day = reading.getDateTime();
-            String key = RedisSchema.getSiteStatsKey(siteId, day);
-
-            updateBasic(jedis, key, reading);
-        }
-    }
-
-    // A naive implementation of update. This implementation has
-    // potential race conditions and makes several round trips to Redis.
-    private void updateBasic(Jedis jedis, String key, MeterReading reading) {
-        String reportingTime = ZonedDateTime.now(ZoneOffset.UTC).toString();
-        jedis.hset(key, SiteStats.reportingTimeField, reportingTime);
-        jedis.hincrBy(key, SiteStats.countField, 1);
-        jedis.expire(key, weekSeconds);
-
-        String maxWh = jedis.hget(key, SiteStats.maxWhField);
-        if (maxWh == null || reading.getWhGenerated() > Double.valueOf(maxWh)) {
-            jedis.hset(key, SiteStats.maxWhField,
-                    String.valueOf(reading.getWhGenerated()));
-        }
-
-        String minWh = jedis.hget(key, SiteStats.minWhField);
-        if (minWh == null || reading.getWhGenerated() < Double.valueOf(minWh)) {
-            jedis.hset(key, SiteStats.minWhField,
-                    String.valueOf(reading.getWhGenerated()));
-        }
-
-        String maxCapacity = jedis.hget(key, SiteStats.maxCapacityField);
-        if (maxCapacity == null || getCurrentCapacity(reading) > Double.valueOf(maxCapacity)) {
-            jedis.hset(key, SiteStats.maxCapacityField,
-                    String.valueOf(getCurrentCapacity(reading)));
-        }
-    }
-
-    // Challenge #3
-    private void updateOptimized(Jedis jedis, String key, MeterReading reading) {
-        // START Challenge #3
-        // END Challenge #3
-    }
-
-    private Double getCurrentCapacity(MeterReading reading) {
-        return reading.getWhGenerated() - reading.getWhUsed();
-    }
+	private final int weekSeconds = 60 * 60 * 24 * 7;
+	private final JedisPool jedisPool;
+	private final CompareAndUpdateScript compareAndUpdateScript;
+
+	public SiteStatsDaoRedisImpl( JedisPool jedisPool ) {
+		this.jedisPool = jedisPool;
+		this.compareAndUpdateScript = new CompareAndUpdateScript( jedisPool );
+	}
+
+	// Returns the site stats for the current day
+	@Override
+	public SiteStats findById( long siteId ) {
+		return findById( siteId, ZonedDateTime.now() );
+	}
+
+	@Override
+	public SiteStats findById( long siteId, ZonedDateTime day ) {
+		try ( Jedis jedis = jedisPool.getResource() ) {
+			String key = RedisSchema.getSiteStatsKey( siteId, day );
+			Map<String, String> fields = jedis.hgetAll( key );
+			if ( fields == null || fields.isEmpty() ) {
+				return null;
+			}
+			return new SiteStats( fields );
+		}
+	}
+
+	@Override
+	public void update( MeterReading reading ) {
+		try ( Jedis jedis = jedisPool.getResource() ) {
+			Long siteId = reading.getSiteId();
+			ZonedDateTime day = reading.getDateTime();
+			String key = RedisSchema.getSiteStatsKey( siteId, day );
+
+			updateOptimized( jedis, key, reading );
+		}
+	}
+
+	// A naive implementation of update. This implementation has
+	// potential race conditions and makes several round trips to Redis.
+	private void updateBasic( Jedis jedis, String key, MeterReading reading ) {
+		String reportingTime = ZonedDateTime.now( ZoneOffset.UTC ).toString();
+		jedis.hset( key, SiteStats.reportingTimeField, reportingTime );
+		jedis.hincrBy( key, SiteStats.countField, 1 );
+		jedis.expire( key, weekSeconds );
+
+		String maxWh = jedis.hget( key, SiteStats.maxWhField );
+		if ( maxWh == null || reading.getWhGenerated() > Double.valueOf( maxWh ) ) {
+			jedis.hset( key, SiteStats.maxWhField, String.valueOf( reading.getWhGenerated() ) );
+		}
+
+		String minWh = jedis.hget( key, SiteStats.minWhField );
+		if ( minWh == null || reading.getWhGenerated() < Double.valueOf( minWh ) ) {
+			jedis.hset( key, SiteStats.minWhField, String.valueOf( reading.getWhGenerated() ) );
+		}
+
+		String maxCapacity = jedis.hget( key, SiteStats.maxCapacityField );
+		if ( maxCapacity == null || getCurrentCapacity( reading ) > Double.valueOf( maxCapacity ) ) {
+			jedis.hset( key, SiteStats.maxCapacityField, String.valueOf( getCurrentCapacity( reading ) ) );
+		}
+	}
+
+	// Challenge #3
+	private void updateOptimized( Jedis jedis, String key, MeterReading reading ) {
+		String reportingTime = ZonedDateTime.now( ZoneOffset.UTC ).toString();
+
+		jedis.hset( key, SiteStats.reportingTimeField, reportingTime );
+		jedis.hincrBy( key, SiteStats.countField, 1 );
+		jedis.expire( key, weekSeconds );
+
+		Transaction transaction = jedis.multi();
+
+		compareAndUpdateScript.updateIfGreater( transaction, key, SiteStats.maxWhField, reading.getWhGenerated() );
+		compareAndUpdateScript.updateIfLess( transaction, key, SiteStats.minWhField, reading.getWhGenerated() );
+		compareAndUpdateScript.updateIfGreater( transaction, key, SiteStats.maxCapacityField, getCurrentCapacity( reading ) );
+
+		transaction.exec();
+		transaction.close();
+	}
+
+	private Double getCurrentCapacity( MeterReading reading ) {
+		return reading.getWhGenerated() - reading.getWhUsed();
+	}
 }