If x is a sum of all even integers on the interval 13...65 and y is their number, what is the GCD (x, y)?  Choose the correct choice:
A) 1
B) 13
C) 26
D) 52
E) 1014
x = 14 + 16 + ... + 64 = (largest + smallest)/2 *(# of terms) = (14 + 64)/2*26 = 39*26.   GCD of 26 and 39*26 is 26.   Answer: 26.
<result>C</result>
If x is a sum of all even integers on the interval 13...65 and y is their number, what is the GCD (x, y)?