Three rugs have a combined area of 204 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 ? Choose the correct choice from the following choices:
A) 18 square meters  B) 20 square meters  C) 24 square meters  D) 28 square meters  E) 30 square meters

Rationale: "total = rug 1 + rug 2 + rug 3 - { overlap of exactly 2 rugs } - 2 * { overlap of exactly 3 rugs } 140 = 204 - 24 - 2 * { overlap of exactly 2 rugs } - - > { overlap of exactly 3 rugs } = 20 . answer : b ."
Answer: B