For the past n days, the average (arithmetic mean) daily production at a company was 50 units. If today's production of 60 units raises the average to 55 units per day, what is the value of n ? Choose the correct choice from the following:	A) 30	B) 18	C) 10	D) 9	E) 1

Rationale: "( average production for n days ) * n = ( total production for n days ) - - > 50 n = ( total production for n days ) ; ( total production for n days ) + 60 = ( average production for n + 1 days ) * ( n + 1 ) - - > 50 n + 60 = 55 * ( n + 1 ) - - > n = 1 . answer : e ."
Answer: E