Task: Question Answering
Input (English): Background Paragraph: Storing large volumes of data – When storing XML to either file or database, the volume of data a system produces can often exceed reasonable limits, with a number of detriments: the access times go up as more data is read, CPU load goes up as XML data takes more power to process, and storage costs go up. By storing XML data in Fast Infoset format, data volume may be reduced by as much as 80 percent. 
Story: Gary had a lot of storing to do on his computer. At 1 PM, he stored 1 Gigabyte of XML data to the main file. At 2 PM, he stored 2 Gigabytes of XML data to the main file. At 3 PM, he didn't store anything. At 4 PM, he stored 3 Gigabytes of XML data to the main file. At 5 PM, he stored 4 Gigabytes of XML data to the main file. At 6 PM, he did nothing. At 7 PM, he got dinner. At 8 PM, he stored 5 Gigabytes of XML data to the main file. He went to sleep at 9 PM and had to start again in the morning. 
Question: What hour did storage costs go up: 4 PM or 6 PM?
Output (English): 4 PM.