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.

[EX Q]: Problem: if the average ( arithmetic mean ) of a and b is 45 and the average of b and c is 80, what is the value of c − a ?
Options: a. 25, b. 60, c. 90, d. 140, e. it can not be determined from the information given.
[EX A]: b

[EX Q]: Problem: the perimeter of a triangle is 40 cm and the inradius of the triangle is 2.5 cm. what is the area of the triangle ?
Options: a. 87 cm 2, b. 28 cm 2, c. 98 cm 2, d. 26 cm 2, e. 50 cm 2
[EX A]: e

[EX Q]: Problem: a train running at a speed of 36 kmph crosses an electric pole in 12 seconds. in how much time will it cross a 350 m long platform ?
Options: a. 44 sec, b. 49 sec, c. 42 sec, d. 47 sec, e. none of these
[EX A]:
d