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: bottle r contains 350 capsules and costs $ 6.25. bottle t contains 130 capsules and costs $ 2.99. what is the difference between the cost per capsule for bottle r and the cost per capsule for bottle t ?
Options: a. $ 0.25, b. $ 0.12, c. $ 0.0052, d. $ 0.003, e. $ 0.002
[EX A]: c

[EX Q]: Problem: an optometrist charges $ 150 per pair for soft contact lenses and $ 85 per pair for hard contact lenses. last week she sold 5 more pairs of soft lenses than hard lenses. if her total sales for pairs of contact lenses last week were $ 1,220, what was the total number of pairs of contact lenses that she sold ?
Options: a. 9, b. 13, c. 15, d. 17, e. 19
[EX A]: a

[EX Q]: Problem: on a certain road 10 % of the motorists exceed the posted speed limit and receive speeding tickets, but 50 % of the motorists who exceed the posted speed limit do not receive speeding tickets. what percent of the motorists on the road exceed the posted speed limit ?
Options: a. 10.5 %, b. 12.5 %, c. 15 %, d. 22 %, e. 20 %
[EX A]:
e