Let n be a positive odd integer. (a) prove that there is a 1-to-1 correspondence between the divisors of n which are squareroot n. (this part does not require n to be odd.) (b) prove that there is a 1-to-1 correspondence between all of the divisors of n which are greaterthanorequalto squareroot n and all the ways of writing n as a difference s^2-t^2 of two squares of nonnegative integers. (for example, 15 has two divisors greaterthanorequalto squareroot n15, and 15 = 4^2 - 1^2 = 8^2 - 7^2.) (c) list all of the ways of writing 945 as a difference of nonnegative integers.