If integer k is equal to the sum of all even multiples of 5 between 300 and 610, what is the greatest prime factor of k?  Options:
A) 32 B) 7 C) 11 D) 13 E) 17

Rationale: "if we break down what the stem is asking what is the sum of all mult of 10 between 300 and 610 . using arithmetic progression to find n : 610 = 300 + ( n - 1 ) 10 310 + 10 = 10 n 320 = 10 n = > n = 32 the sum would be : 32 * mean mean = [ 610 + 300 ] / 2 = 455 32 * 455 a"
Answer: A