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.
--------
Question: Problem: the probability of two events a and b are 0.25 and 0.40 respectively. the probability that both a and b occur is 0.15. the probability that neither a nor b occur is _________
Options: a. 0.45, b. 0.4, c. 0.5, d. 0.05, e. 0.6

Answer: c

Question: Problem: a shopkeeper sells 500 metres of cloth for rs. 18000 at a loss of rs. 5 per metre. find his cost price for one metre of cloth ?
Options: a. 12, b. 27, c. 29, d. 50, e. 41

Answer: e

Question: Problem: if the average ( arithmetic mean ) of a and b is 45 and the average of b and c is 50, what is the value of c a ' a ?
Options: a. 25, b. 10, c. 90, d. 14, e. it can not be determined from the information given

Answer:
b