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: the cost of 8 dozen pencil and 2 dozen note book is 520 rupee. if cost of 3 pencil and 4 note book is 60 rupee, then sum of the cost of 1 pencil and 1 note book will be ( in rupee.
Options: a. rs 13.51, b. rs 15.51, c. rs 16.51, d. rs 14.51, e. rs 17.51
[A]: b

[Q]: Problem: the salary of a person was reduced by 14 %. by what percent should his reduced salary be raised so as to bring it at par with his original salary ?
Options: a. 10 %, b. 16.3 %, c. 13.7 %, d. 15.1 %, e. 12.3 %
[A]: b

[Q]: Problem: walking at 4 / 5 of her normal speed, a worker is 10 minutes later than usual in reaching her office. the usual time ( in minutes ) taken by her to cover the distance between her home and her office is
Options: a. 30, b. 35, c. 40, d. 45, e. 50
[A]:
c