On day one, a store sold 86 cups. On each of the next d days, the company sold 50 cups. If the average daily sales of cups over this time period (including day one) is 53 cups, what is the value of d? Choose the correct choice from the following answers
A) 9 B) 10 C) 11 D) 12 E) 13

Rationale: 86 + 50 d = 53 ( d + 1 ) . 3 d = 33 . d = 11 . the answer is c .
Answer: C