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: what is the rate percent when the simple interest on rs. 810 amount to rs. 155 in 4 years ?
Options: a. 4.78, b. 4.68, c. 4.58, d. 4.48, e. 4.38

A: a
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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
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Q: Problem: how many cones of radius 4 m, height 2 m can be formed from a cylinder of 12 m radius, 10 m height :
Options: ['a. 135', 'b. 125', 'c. 145', 'd. 115', 'e. 155']

A:
a
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