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: a couple who own an appliance store discover that if they advertise a sales discount of 10 % on every item in the store, at the end of one month the number of total items sold increases 15 %. their gross income from sales for one month increases by what percent ?
Options: a. 1.5 %, b. 2.5 %, c. 3.5 %, d. 4.5 %, e. 5.5 %

A: c
****
Q: Problem: an aeroplane covers a certain distance at a speed of 150 kmph in 2 hours. to cover the same distance in 1 2 / 3 hours, it must travel at a speed of :
Options: a. 1300 kmph, b. 160 kmph, c. 180 kmph, d. 1080 kmph, e. none

A: c
****
Q: Problem: how many zeroes are there at the end of the number n, if n = 70 ! + 140 ! ?
Options: a. 8, b. 12, c. 16, d. 20, e. 24

A:
c
****