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 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

Answer: c


Question: Problem: if price of t. v set is reduced by 20 %, then its sale increases by 80 %, find net effect on sale value
Options: a. 44, b. 45, c. 46, d. 47, e. 48

Answer: a


Question: Problem: a 150 meter long train crosses a man standing on the platform in 3 sec. what is the speed of the train ?
Options: a. 176 kmph, b. 108 kmph, c. 176 kmph, d. 134 kmph, e. 180 kmph

Answer:
e