Ifaequals the sum of the even integers from 2 to 60, inclusive, andbequals the sum of the odd integers from 1 to 59, inclusive, what is the value of a - b ?
Choose the correct choice.
A) 1
B) 10
C) 30
D) 20
E) 21

Rationale: "this is a solution from beatthegmat : even numbers : ( 60 - 2 ) / 2 + 1 = 30 even integers . ( 60 + 2 ) / 2 = 31 is the average of the even set . sum = avg * ( # of elements ) = 31 * 30 = 930 = a odd numbers : ( 59 - 1 ) / 2 + 1 = 30 odd integers . ( 59 + 1 ) / 2 = 30 is the average of the odd set . sum = avg * ( # of elements ) = 30 * 30 = 900 = b a - b = 930 - 900 = 30 . answer : c"
Answer: C