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: given that p is a positive even integer with a positive units digit, if the units digit of p ^ 3 minus the units digit of p ^ 2 is equal to 0, what is the units digit of p + 4 ?
Options: a. 7, b. 8, c. 10, d. 11, e. 12

A: c
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Q: Problem: what is the normal price of an article sold at $ 72 after two successive discounts of 10 % and 20 % ?
Options: a. $ 92, b. $ 96, c. $ 100, d. $ 104, e. $ 108

A: c
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Q: Problem: the average age of students of a class is 15.8 years. the average age of boys in the class is 16.7 years and that of the girls is 15.4 years. the ration of the number of boys to the number of girls in the class is :
Options: a. 2: 5, b. 2: 3, c. 2: 4, d. 2: 1, e. 4: 9

A:
e
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