In how many ways can two integers be selected from 60 consecutive positive integers so that their sum is even?

For which of these functions is function composition commutative with ƒ(x) = (x + 1 /3x − 2) ? a - g(x) = (3x − 2/x + 1)b - g(x) = (3x − 3/x + 2)c - g(x) = (2x + 1/3x − 1)d - g(x) = (2x − 1/3x + 1)