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: last year elaine spent 20 % of her annual earnings on rent. this year she earned 35 % more than last year and she spent 30 % of her annual earnings on rent. the amount she spent on rent this year is what percent of the amount spent on rent last year ?
Options: a. 202.5, b. 194.5, c. 197.5, d. 182.5, e. 177.5

A: a
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Q: Problem: p can do a work in the same time in which q and r together can do it. if p and q work together, the work can be completed in 10 days. r alone needs 35 days to complete the same work. then q alone can do it in
Options: a. 20, b. 22, c. 25, d. 28, e. 30

A:
d
****