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.

Problem: a train 50 m long takes 6 sec to cross a man walking at 5 kmph in a direction opposite to that of the train. find the speed of the train ?
Options: a. 15 kmph, b. 25 kmph, c. 35 kmph, d. 45 kmph, e. 55 kmph
b

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
b

Problem: the average of 11 numbers is 60. out of 11 numbers the average of first 6 no. is 98, and last 6 numbers is 65 then find 6 th number ?
Options: a. a. 318, b. b. 65, c. c. 58, d. d. 62, e. e. 48
a