Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

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. 50, b. 90, c. 80, d. 28, e. 93
c

Problem: a boat having a length 8 m and breadth 2 m is floating on a lake. the boat sinks by 1 cm when a man gets on it. the mass of the man is :
Options: a. 12 kg, b. 60 kg, c. 72 kg, d. 160 kg, e. none of these
d

Problem: 1257 1275 1527................ + 7521 the addition problem above shows 4 of the 24 different integers that can be formed by using each of the digits 1, 25 and 7 exactly once in each integer. what is the sum t of the 24 integers ?
Options: a. 26996, b. 44406, c. 60444, d. 66660, e. 99990

e