Task: Question Answering
Input (English): Problem: a person purchases 90 clocks and sells 40 clocks at a gain of 10 % and 50 clocks at a gain of 20 %. if he sold all of them at a uniform profit of 15 %, then he would have got rs. 40 less. the cost price of each clock is: ?
Options: a. 40, b. 60, c. 80, d. 67, e. 30
Output (English): c