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: the total marks obtained by a student in mathematics and physics is 50 and his score in chemistry is 20 marks more than that in physics. find the average marks scored in mathamatics and chemistry together.
Options: a. 15, b. 25, c. 35, d. 45, e. 55
[EX A]: c

[EX Q]: Problem: if the simple interest on a certain amount in at 4 % rate 5 years amounted to rs. 2240 less than the principal. what was the principal ?
Options: a. 1500, b. 2500, c. 2507, d. 2800, e. 11500
[EX A]: d

[EX Q]: Problem: a woman bought a pack of 36 eggs, but the seller told her that there were 3 rotten eggs in the pack. she forgot it and begun to prepare a recipe that needs 2 eggs. what is the probability that both choosen eggs will be rotten ?
Options: a. 1 / 210, b. 2 / 210, c. 3 / 210, d. 1 / 119, e. 2 / 119
[EX A]:
a