Given the task definition and input, reply with output. 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: three rugs have a combined area of 212 square meters. by overlapping the rugs to cover floor area of 140 square meters, the area that is covered by exactly two layers of rug is 24 square meters. what is the area that is covered with three layers of rug ?
Options: a. 18 square meters, b. 20 square meters, c. 24 square meters, d. 28 square meters, e. 30 square meters
c