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 the simple interest on a certain sum of money for 6 years is one – fifth of the sum, then the rate of interest per annum is
Options: a. 3.3 %, b. 7.2 %, c. 6.1 %, d. 5.0 %, e. 3.1 %

A: a
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Q: Problem: last year elaine spent 20 % of her annual earnings on rent. this year she earned 20 % 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. 185.5, b. 180.0, c. 167.5, d. 172.5, e. 177.5

A: b
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Q: Problem: in the coordinate plane, line a has a slope of - 2 and an x - intercept of 2. line b has a slope of 5 and a y - intercept of - 10. if the two lines intersect at the point ( a, b., what is the sum a + b ?
Options: a. 0, b. 1, c. 2, d. 3, e. 4

A:
c
****