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.

Problem: how many 4 - digit numbers that do not contain the digits 2, 3, 4, 5, 6, or 7 are there ?
Options: a. 168, b. 176, c. 184, d. 192, e. 200
d

Problem: how many prime numbers are between 76 / 8 and 124 / 5 ?
Options: a. 1, b. 2, c. 3, d. 4, e. 5
e

Problem: a grocery store bought some mangoes at a rate of 5 for a dollar. they were separated into two stacks, one of which was sold at a rate of 5 for a dollar and the other at a rate of 5 for a dollar. what was the ratio of the number of mangoes in the two stacks if the store broke even after having sold all of its mangoes ?
Options: a. 1: 1, b. 1: 5, c. 2: 3, d. 1: 2, e. 2: 5

a