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: if a man lost 8 % by selling oranges at the rate of 25 a rupee at how many a rupee must he sell them to gain 25 % ?
Options: a. 20, b. 15, c. 18.4, d. 20, e. 12.8
c

Problem: if the ratio of two number is 6: 7 and lcm of the number is 450 then what is the number.
Options: a. 11, b. 20, c. 25, d. 30, e. 35
a

Problem: the end of a blade on an airplane propeller is 10 feet from the center. if the propeller spins at the rate of 1,320 revolutions per second, how many miles will the tip of the blade travel in one minute ? ( 1 mile = 5,280 feet )
Options: a. 200 π, b. 240 π, c. 300 π, d. 480 π, e. 1,200 π

c