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.

[Q]: Problem: a walks at 10 kmph and 4 hours after his start, b cycles after him at 20 kmph. how far from the start does b catch up with a ?
Options: a. 100 km, b. 150 km, c. 80 km, d. 120 km, e. 200 km
[A]: c


[Q]: Problem: x does a work in 20 days. y does the same work in 40 days. in how many days they together will do the same work ?
Options: a. 10, b. 12, c. 20, d. 30, e. 13.33
[A]: e


[Q]: Problem: in 1970 there were 8,902 women stockbrokers in the united states. by 1978 the number had increased to 23,947. approximately what was the percent increase ?
Options: a. 45 %, b. 125 %, c. 145 %, d. 150 %, e. 169 %
[A]:
e