Gmat Data Sufficiency

题目

Gmat Data Sufficiency
"the range of the monthly closing balance"如何理解?
eg.Beginning in January of last year,Carl made deposits of USD120 into his account on th 15th of each month for several consecutive months and then made withdrawals of USD50 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 USD2600,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 Apr was less than USD2625.
(2)Last year the closing balance of Carl's account for Jun was less than USD2675.
Answer:C
最好能翻译并给出中文详细解答.

答案

the range of the monthly closing balances 月结算余额的范围 题目的意思是 从去年1月开始C每个月15号向账户中存入150刀,连续存N个月；然后从N+1月开始到12月每个月取出50刀.现在一直去年5月的月结算余额是2600刀,...