3 friends A, B, C went for week end party to McDonald’s restaurant and there they measure there weights in some order In 7 rounds. A, B, C, AB, BC, AC, ABC. Final round measure is 170kg then find the average weight of all the 7 rounds? Options: A) 97.1 kgs B) 88.5 kgs C) 86.5 kgs D) 67.5 kgs E) 88.2 kgs

Rationale: "average weight = [ ( a + b + c + ( a + b ) + ( b + c ) + ( c + a ) + ( a + b + c ) ] / 7 = 4 ( a + b + c ) / 7 = 4 x 170 / 7 = 97.1 kgs answer : a"
Answer: A