Write and prove correct a procedure in Scheme binom which inputs a positive integer n and which returns a function of integer k and numbers a and b such that ((binomial n) k a b) is the kth term in the binomial expansion of (a + b)^n.

You will recall that this term is the product of the kth entry in the nth row of Pascal's triangle with a^k and b^(n - k).

You will need to write - and prove - a procedure in Scheme to compute a given entry in Pascal's triangle, as well as the procedure binom.