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: a person ' s present age is two - fifth of the age of his mother. after 8 years, he will be one - half of the age of his mother. how old is the mother at present
Options: a. 38, b. 40, c. 42, d. 44, e. 45

Answer: b


Question: Problem: a merchant marks his goods up by 30 % and then offers a discount of 10 % on the marked price. what % profit does the merchant make after the discount ?
Options: a. 17 %, b. 25 %, c. 69 %, d. 31 %, e. 19 %

Answer: a


Question: Problem: if 10 gallons of grape juice are added to 40 gallons of a mixture, which contains 20 percent grape juice then what percent of the resulting mixture is grape juice ?
Options: a. 14 %, b. 25 %, c. 28 %, d. 36 %, e. 50 %

Answer:
d