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: a boat having a length 8 m and breadth 2 m is floating on a lake. the boat sinks by 1 cm when a man gets on it. the mass of the man is :
Options: a. 12 kg, b. 60 kg, c. 72 kg, d. 160 kg, e. none of these

Ex Output:
d


Ex Input:
Problem: on a certain day, orangeade was made by mixing a certain amount of orange juice with an equal amount of water. on the next day, orangeade was made by mixing the same amount of orange juice with twice the amount of water. on both days, all the orangeade that was made was sold. if the revenue from selling the orangeade was the same for both days and if the orangeade was sold at $ 0.30 per glass on the first day, what was the price per glass on the second day ?
Options: a. $ 0.15, b. $ 0.20, c. $ 0.30, d. $ 0.40, e. $ 0.45

Ex Output:
b


Ex Input:
Problem: rebecca ' s annual income is $ 15, and jimmy ' s annual income is $ 18. by how much must rebecca ' s annual income increase so that it constitutes 50 % of rebecca and jimmy ' s combined income ?
Options: a. 7, b. 8, c. 9, d. 3, e. 10

Ex Output:

d