The sum of the non-prime numbers between 20 and 30, non-inclusive, is
Choose the correct choice from the following:
A) 173 B) 185 C) 197 D) 209 E) 221

Rationale: "sum of consecutive integers from 21 to 29 , inclusive = = = = > ( a 1 + an ) / 2 * # of terms = ( 21 + 29 ) / 2 * 9 = 25 * 9 = 225 sum of non - prime numbers b / w 20 and 30 , non inclusive = = = > 225 - 52 ( i . e . , 23 + 29 , being the prime # s in the range ) = 173 answer : a"
Answer: A