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

[Q]: Problem: a lady grows broccoli in her garden that is in the shape of a square. each broccoli takes 1 square foot of area in her garden. this year, she has increased her output by 79 broccoli when compared to last year. the shape of the area used for growing the broccoli has remained a square in both these years. how many broccoli did she produce this year ?
Options: ['a. 1600', 'b. 1500', 'c. 1650', 'd. 1700', 'e. can not be determined']
[A]: a

[Q]: Problem: the price of an item is discounted 10 percent on day 1 of a sale. on day 2, the item is discounted another 10 percent, and on day 3, it is discounted an additional 30 percent. the price of the item on day 3 is what percentage of the sale price on day 1 ?
Options: a. 28 %, b. 63 %, c. 64.8 %, d. 70 %, e. 72 %
[A]:
b