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.

Input: Consider Input: Problem: in traveling from a dormitory to a certain city, a student went 1 / 3 of the way by foot, 3 / 5 of the way by bus, and the remaining 2 kilometers by car. what is the distance, in kilometers, from the dormitory to the city ?
Options: a. 30, b. 45, c. 60, d. 90, e. 120

Output: a

Input: Consider Input: Problem: in a certain pond, 50 fish were caught, tagged, and returned to the pond. a few days later, 50 fish were caught again, of which 5 were found to have been tagged. if the percent of tagged fish in the second catch approximates the percent of tagged fish in the pond, what is the approximate number of fish in the pond ?
Options: a. 400, b. 500, c. 1,250, d. 2,500, e. 10,000

Output: b

Input: Consider Input: Problem: two bullet train s 140 m and 180 m long run at the speed of 60 km / hr and 40 km / hr respectively in opposite directions on parallel tracks. the time ( in seconds ) which they take to cross each other, is :
Options: a. 15.8 sec., b. 11.52 sec., c. 11.8 sec., d. 10.8 sec., e. 08.8 sec.
Output: b