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 copy machine, working at a constant rate, makes 35 copies per minute. a second copy machine, working at a constant rate, makes 65 copies per minute. working together at their respective rates, how many copies do the two machines make in half an hour ?
Options: a. 3,000, b. 2,700, c. 4,500, d. 5,400, e. 324,000
[EX A]: a

[EX Q]: Problem: a man spends 2 / 5 of his salary on house rent, 3 / 10 of his salary on food and 1 / 8 of his salary on convenience he has rs. 1400 left with him, find his expenditure on food and conveyance.
Options: a. 1000, b. 3000, c. 4000, d. 2000, e. 5000
[EX A]: a

[EX Q]: Problem: one fourth of a solution that was 8 % sugar by weight was replaced by a second solution resulting in a solution that was 16 percent sugar by weight. the second solution was what percent sugar by weight ?
Options: a. 74 %, b. 52 %, c. 40 %, d. 18 %, e. 8.5 %
[EX A]:
c