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: Porfirio had a busy day storing XML. At 9 AM, he stored 203 Gigabytes to the database. At 10 AM, he stored 303 Gigabytes to the database. At 11 AM, he stored 403 Gigabytes to the database. At 12 PM, he got lunch. At 1 PM, he stored 503 Gigabytes to the database. At 2 PM, he stored 603 Gigabytes to the database. At 3 PM, she went to sleep to finish storing XML later that night. 
Question: What time did storage costs go up:  10 AM or 12 PM?
10 AM.