A certain list consists of 21 different numbers. If n is in the list and n is 3 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?	Choose the correct choice from the following options:
A) 1 / 20  B) 1 / 6  C) 1 / 5  D) 4 / 21  E) 3 / 23

Rationale: "series : a 1 , a 2 . . . . a 20 , n sum of a 1 + a 2 + . . . + a 20 = 20 * x ( x = average ) so , n = 3 * x hence , a 1 + a 2 + . . + a 20 + n = 23 x so , the fraction asked = 3 x / 23 x = 3 / 23 answer e"
Answer: E