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.
--------
Question: Problem: what is the rate percent when the simple interest on rs. 720 amount to rs. 180 in 4 years ?
Options: a. 6.25, b. 7.25, c. 8.25, d. 9.25, e. 10.25

Answer: a


Question: Problem: what number must be added to 6, 16 and 8 to get an average of 13 ?
Options: a. 23, b. 22, c. 44, d. 33, e. 55

Answer: b


Question: Problem: a garrison of 400 men had a provision for 31 days. after 26 days 275 persons re - enforcement leave the garrison. find the number of days for which the remaining ration will be sufficient ?
Options: a. 16 days, b. 45 days, c. 10 days, d. 17 days, e. 18 days

Answer:
a