Ifaequals the sum of the even integers from 2 to 80, inclusive, andbequals the sum of the odd integers from 1 to 79, inclusive, what is the value of a - b ?	Choose the correct answer
A) 1	B) 10	C) 19	D) 40	E) 21

Rationale: "this is a solution from beatthegmat : even numbers : ( 80 - 2 ) / 2 + 1 = 40 even integers . ( 80 + 2 ) / 2 = 41 is the average of the even set . sum = avg * ( # of elements ) = 41 * 40 = 1640 = a odd numbers : ( 79 - 1 ) / 2 + 1 = 40 odd integers . ( 79 + 1 ) / 2 = 40 is the average of the odd set . sum = avg * ( # of elements ) = 40 * 40 = 1600 = b a - b = 1640 - 1600 = 40 . answer : d"
Answer: D