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: at what rate percent per annum will a sum of money double in 6 years.
Options: a. 12.5 %, b. 13.5 %, c. 11.5 %, d. 14.5 %, e. 16.6 %

A: e
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Q: Problem: a train running at the speed of 20 km / hr crosses a post in 10 seconds. what is the length of the train ?
Options: a. 150, b. 250, c. 415, d. 200, e. 312

A: d
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Q: Problem: every disk in a bag is either blue, yellow or green. the ratio of blue disks to yellow disks to green disks in this bag is 3: 7: 8. if the total number of disks in the bag is 144, how many more green disks than blue disks are in the bag ?
Options: a. 25, b. 28, c. 30, d. 35, e. 40

A:
e
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