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.

Q: Problem: if y exceeds x by 25 %, then x is less than y by ?
Options: a. 28 %, b. 21 %, c. 20 %, d. 30 %, e. 29 %

A: c
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Q: 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

A: c
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Q: Problem: find the average of all prime numbers between 40 and 80.
Options: a. 59.4, b. 56, c. 39.8, d. 44.9, e. none

A:
a
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