If each term in the sum: ( a1 + a2 + ..... + an ) is either 7 or 77 and the sum equals 350, which of the following could be equal to n ?

(A) 38
(B) 39
(C) 40
(D) 41
(E) 42

Correct answer: (C)

Any help regarding this is appreciated.

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the search box is in the upper right hand corner. to use it, just type in two or three conspicuous words or numbers from the problem statement. (for this problem, typing "77 350 sum" finds the two relevant threads without uncovering any irrelevant noise.)

also, follow the protocol when titling your posts: first 8 or so words of the problem statement
thank you