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: the circumference of the front wheel of a cart is 30 ft long and that of the back wheel is 32 ft long. what is the distance traveled by the cart, when the front wheel has done five more revolutions than the rear wheel ?
Options: a. 20 ft, b. 25 ft, c. 750 ft, d. 900 ft, e. 2400 ft
[EX A]: e

[EX Q]: Problem: water is leaking out from a cylinder container at the rate of 0.31 m ^ 3 per minute. after 10 minutes, the water level decreases 1 / 9 meters. what is value of the radius in meters ?
Options: a. 2, b. 3, c. 4, d. 6, e. 9
[EX A]: b

[EX Q]: Problem: the average monthly income of p and q is rs. 2050. the average monthly income of q and r is rs. 5250 and the average monthly income of p and r is rs. 6200. the monthly income of r is :
Options: a. 5100, b. 4900, c. 9400, d. 1500, e. 3200
[EX A]:
c