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: two trains of equal length are running on parallel lines in the same directions at 46 km / hr. and 36 km / hr. the faster trains pass the slower train in 72 seconds. the length of each train is :
Options: a. 82 m, b. 50 m, c. 72 m, d. 100 m, e. none of these

A: d
****
Q: Problem: rajani has to read a book of 445 pages. she has already read the first 157 pages of the book and if she reads 24 pages of the book everyday then how long will she take now to complete the book ?
Options: a. 25 days, b. 20 days, c. 46 days, d. 21 days, e. none of these

A: e
****
Q: Problem: how long will a boy take to run round a square field of side 35 meters, if he runs at the rate of 9 km / hr ?
Options: a. 22, b. 38, c. 37, d. 56, e. 28

A:
d
****