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The average of four numbers A, B, C and D is 40. The average of four numbers A, B, E and F is also 40. (A, B are common). Which of the following must be true ?
- A(A + B) $\neq$ (C + D)
- B(C + D) = (E + F)
- CEither C = E or F; and F or E
- DC = E and D = F
Answer not set