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.

Example Input: Problem: when jessica withdrew $ 200 from her bank account, her account balance decreased by 2 / 5. if she deposits an amount equal to 2 / 3 of the remaining balance, what will be the final balance in her bank account ?
Options: a. 300, b. 375, c. 400, d. 500, e. 575
Example Output: d

Example Input: Problem: in what ratio must a grocer mix two varieties of pulses costing rs. 15 and rs. 20 per kg respectively so as to get a mixture worth rs. 16.50 per kg ?
Options: a. 3: 7, b. 5: 7, c. 7: 3, d. 7: 5, e. none
Example Output: c

Example Input: 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
Example Output:
c