For the past n days, the average (arithmetic mean) daily production at a company was 60 units. If today's production of 90 units raises the average to 62 units per day, what is the value of n ? Select the correct option:  A) 30  B) 14  C) 10  D) 9  E) 7

Rationale: "( average production for n days ) * n = ( total production for n days ) - - > 60 n = ( total production for n days ) ; ( total production for n days ) + 90 = ( average production for n + 1 days ) * ( n + 1 ) - - > 60 n + 90 = 62 * ( n + 1 ) - - > n = 14 . or as 30 extra units increased the average for n + 1 days by 2 units per day then 30 / ( n + 1 ) = 2 - - > n = 14 . answer : b ."
Answer: B