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 area of a circle decreases by 66 %, then the radius of a circle decreases by
Options: a. 20 %, b. 18 %, c. 36 %, d. 64 %, e. none of these
[EX A]: e

[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: the cost of 3 pens and 5 pencils is rs. 150. also the cost of one pen and one pencil is in the ratio of 5: 1 respectively. what is the cost of one dozen pens ?
Options: a. rs. 200, b. rs. 250, c. rs. 300, d. rs. 450, e. none of these
[EX A]:
d