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.

[EX Q]: Problem: a merchant marks goods up by 80 % and then offers a discount on the marked price. the profit that the merchant makes after offering the discount is 35 %. what % discount did the merchant offer ?
Options: a. 20 %, b. 25 %, c. 30 %, d. 35 %, e. 40 %
[EX A]: b

[EX Q]: Problem: if x and y are positive integers and 3 + x + y + xy = 17, what is the value of x + y ?
Options: a. 3, b. 5, c. 6, d. 8, e. 9
[EX A]: c

[EX Q]: Problem: a person is traveling at 75 km / hr and reached his destiny in 4 hr then find the distance ?
Options: a. 300 km, b. 200 km, c. 250 km, d. 400 km, e. 220 km
[EX A]:
a