求助新东方数学讲义的一道题关于data sufficiency的

Nicolexin

Beginning in January of 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?

sdcar2010

Where are the two conitions to choose from?

Nicolexin

啊，对不起，我晕头忘了发了下面是：
（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

Nicolexin

最后算出来了，是5月存，6月取，但是极值的最小值是1月还是最后一月的啊，搞不明白

chasebetter

这道题应该不需要求最小值吧，关键点就是为了确定从几月开始取钱，又因为5月份的结算余额已知，每个月的就都能推算出来了。