instruction:
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.
question:
Problem: a and b together can complete work in 6 days. a alone starts working and leaves it after working for 4 days completing only half of the work. in how many days it can be completed if the remaining job is undertaken by b ?
Options: a. 4, b. 12, c. 5, d. 6, e. 7
answer:
b

question:
Problem: if ( 2 ^ 16 ) ( 25 ^ s ) = 5 ( 10 ^ m ) what is the value of m ?
Options: a. 7, b. 8, c. 15, d. 16, e. 23
answer:
d

question:
Problem: if x / 4 years ago roger was 21 years old and x / 4 years from now he will be 4 x years old, how old will he be 5 x years from now ?
Options: a. 32, b. 35, c. 30, d. 40, e. 70
answer:
e