If x is a sum of all even integers on the interval 23...65 and y is their number, what is the GCD (x, y)?  Choose the correct choice from the following answers:
A) 1
B) 21
C) 26
D) 52
E) 1014
x = 24 + 16 + ... + 64 = (largest + smallest)/2 *(# of terms) = (24 + 64)/2*21= 44*16.   GCD of 21 and 44*21 is 21.   Answer: 21.
<result>B</result>
If x is a sum of all even integers on the interval 23...65 and y is their number, what is the GCD (x, y)?