On the morning of Sept 24, 2020, only three traders (Alex, Barbara, and Christine) had an open position in futures contract for corn with delivery in January 2022. In particular, Alex had a long position in 2 contracts, and Barbara had a short position in 13 contracts. Information about the position of Christine is not given to you. During the day of Sept 24, 2020, the following trades occurred: Alex sold 6 contracts to Barbara Barbara bought 10 contracts from Christine Diane, a new trader, bought X>0 contracts from Christine At the end of Sept 24, the open interest was 9. How many contracts did Diane buy from Christine? Please, write your answer as an integer number. For example, if you answer is 24 contracts, write 24