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 train covers a distance of 100 km in 1 hour. if its speed is decreased by 15 km / hr, the time taken by the car to cover the same distance will be ?
Options: a. 1 hr, b. 1 hr 10 min, c. 50 min, d. 1 hr 30 min, e. 1 hr 45 min

Answer: b

Question: Problem: the ' ' racing magic ' ' takes 120 seconds to circle the racing track once. the ' ' charging bull ' ' makes 40 rounds of the track in an hour. if they left the starting point together, how many minutes will it take for them to meet at the starting point for the second time ?
Options: a. 3, b. 6, c. 9, d. 12, e. 15

Answer: d

Question: Problem: a clock shows the time as 10 a. m. if the minute hand gains 5 minutes every hour, how many minutes will the clock gain by 6 p. m. ?
Options: a. 45 minutes, b. 55 minutes, c. 35 minutes, d. 25 minutes, e. 40 minutes

Answer:
e