DS１問お願いします

題意がつかめなくて困っております。

お忙しいところ恐縮ですが、題意と解法を教えて頂けないでしょうか？

At the beginning of last month, a stationery store had in stock 250 writing pads, which had cost the store $0.75 each. During the same month, the store made only one purchase of writing pads. What was the total amount spent by the store on the writing pads it had in wtock at the end of last month?

(1) Last month the store purchased 150 writing pads for $0.80 each.

(2) Las month the total revenue from the sale of writing pads was $180.

答えは（Ｅ）です。