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: a sum of money at simple interest amounts to rs. 720 after 2 years and to rs. 1020 after a further period of 5 years. the sum is :
Options: a. 400, b. 500, c. 600, d. 700, e. 800
c

Problem: arjun started a business with rs. 20,000 and is joined afterwards by anoop with rs. 30, 000. after how many months did anoop join if the profits at the end of the year are divided equally ?
Options: a. 3, b. 4, c. 5, d. 6, e. 7
b

Problem: a furniture store owner decided to drop the price of her recliners by 20 % to spur business. by the end of the week she had sold 50 % more recliners. what is the percentage increase of the gross ?
Options: a. 10 %, b. 15 %, c. 20 %, d. 25 %, e. 50 %
c