[求助]OG11 diagnostic test 数学27.

27.If the length of Wanda's telephone call was rounded up to the nearest whole minute by her telephone company,then Wanda was charged for how many minutes for her telephone call?
(1) The total charge for Wanda's telephone call was $6.50
(2) Wanda was charged $0.50 more for the first minute of the telephone call than for each minute after the first.

选E.

我选的是C，答案解释没有看懂……