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.
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Question: Problem: the perimeter of a triangle is 40 cm and the inradius of the triangle is 2.5 cm. what is the area of the triangle ?
Options: a. 87 cm 2, b. 28 cm 2, c. 98 cm 2, d. 26 cm 2, e. 50 cm 2

Answer: e


Question: Problem: set a contains all the even numbers between 2 and 50 inclusive. set b contains all the even numbers between 62 and 110 inclusive. what is the difference between the sum of elements of set b and the sum of the elements of set a ?
Options: a. 1500, b. 3100, c. 4400, d. 6200, e. 7400

Answer: a


Question: Problem: for any positive integer n, the sum of the first n positive integers equals n ( n + 1 ) / 2. what is the sum of odd all the integers between 10 and 100 ?
Options: a. 1345, b. 1576, c. 2475, d. 2578, e. 1895

Answer:
c