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: cereal a is 10 % sugar by weight, whereas healthier but less delicious cereal b is 2 % sugar by weight. to make a delicious and healthy mixture that is 3 % sugar, what should be the ratio of cereal a to cereal b, by weight ?
Options: a. 2: 9, b. 2: 7, c. 1: 7, d. 1: 4, e. 1: 3
[EX A]: c

[EX Q]: Problem: the present population of a town is 2000. population increase rate is 20 % p. a. find the population of town after 1 years ?
Options: a. 1000, b. 2400, c. 1500, d. 1600, e. 1250
[EX A]: b

[EX Q]: Problem: a high school has 400 students 1 / 2 attend the airthmetic club, 5 / 8 attend the biology club and 3 / 4 attend the chemistry club. 1 / 8 attend all 3 clubs. if every student attends at least one club how many students attend exactly 2 clubs.
Options: a. 300, b. 200, c. 250, d. 150, e. 160
[EX A]:
c