问大家一道OG上的数学难题

lllmmm

一道DS题
Beginning in January last year, Carl made deposits of 120 into his account on the 15th of each month for several consecutive months and then made withdrawals of 50 from the account on the 15th of each of the remaining months of last year. There were no other transactions in the account last year. If the closing balance of Carl's account for May of last year was 2600, what was the range of the monthly closing balances of Carl's account last year?
(1)Last year the closing balance of Carl's account for April was less than 2625
(2)Last year the closing balance of Carl's account for June was less than 2675
这题实在是不会  请教大家！

lllmmm

太牛了  谢谢了！