Detailed Instructions: 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.
Q: Problem: 6 ) a marketing firm determined that, of 260 households surveyed, 80 used neither brand a nor brand b soap. 60 used only brand a soap and for every household that used both brands of soap, 3 used only brand b soap. how many of the 200 household surveyed used both brands of soap ?
Options: a. a. 15, b. b. 20, c. c. 30, d. d. 40, e. e. 45
A:
c