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 Q]: Problem: a sum of money at simple interest amounts to $ 645 in 3 years and to $ 690 in 4 years. the sum is :
Options: a. $ 153, b. $ 510, c. $ 598, d. $ 549, e. $ 675
[EX A]: b

[EX Q]: Problem: one side of a rectangular field is 14 m and one of its diagonal is 17 m. find the area of the field.
Options: a. 134.4, b. 120, c. 150, d. 180, e. none
[EX A]: a

[EX Q]: Problem: s is a set of 50 consecutive multiples of 2. if the smallest number in s is 56, then the greatest number in s is
Options: a. 198, b. 154, c. 199, d. 102, e. 105
[EX A]:
b