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: the purchase price of an article is $ 48. in order to include 5 % of cost for overhead and to provide $ 12 of net profit, the markup should be
Options: a. 15 %, b. 25 %, c. 30 %, d. 40 %, e. 45 %
c

Problem: if 5 a = 3125, then the value of 5 ( a - 3 ) is :
Options: a. 25, b. 125, c. 625, d. 1625, e. none of these
a

Problem: gold is 10 times as heavy as water and copper is 6 times as heavy as water. in what ratio should these be mixed to get an alloy 8 times as heavy as water ?
Options: a. 3: 2, b. 1: 1, c. 3: 1, d. 5: 2, e. 4: 3

b