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.

Problem: a can do a piece of work in 4 hours; b and c together can do it in 3 hours, while a and c together can do it 2 hours. how long will b alone take to do it ?
Options: a. 8 hours, b. 10 hours, c. 12 hours, d. 24 hours, e. none of these
c

Problem: a 16 % stock yielding 10 % is quoted at :
Options: a. 83.33, b. 110, c. 112, d. 120, e. 160
e

Problem: the list price of an article is rs. 70. a customer pays rs. 56.16 for it. he was given two successive discounts, one of them being 10 %. the other discount is ?
Options: a. 10.85 %, b. 14.85 %, c. 15.85 %, d. 16.85 %, e. 17.85 %

a