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.

Ex Input:
Problem: for each color copy, print shop x charges $ 1.20 and print shop y charges $ 1.70. how much greater is the charge for 40 color copies at print shop y than at print shop x ?
Options: a. $ 14, b. $ 16, c. $ 18, d. $ 20, e. $ 22

Ex Output:
d

Ex Input:
Problem: the average weight of 6 person ' s increases by 4.5 kg when a new person comes in place of one of them weighing 75 kg. what might be the weight of the new person ?
Options: a. 160 kg, b. 175 kg, c. 180 kg, d. 102 kg, e. 190 kg

Ex Output:
d

Ex Input:
Problem: sandy is younger than molly by 6 years. if their ages are in the respective ratio of 7: 9, how old is molly ?
Options: a. 21, b. 24, c. 27, d. 36, e. 45

Ex Output:
c