Let a denote the set of integers that are multiples of 4, let b denote the set of integers that are multiples of 8 and let b denote the set of even integers. thus a = {4k: k elementof z), b = {8k: k elementof z) and b = {2k: k elementof z}. let f: a times a rightarrow b and g: b rightarrow z be functions defined by f((x, y) = xy for x, y elementof a and g(n) = n/2 for n elementof b. (a) show that the composition function g ? f: a times a rightarrow z is defined. (b) for k, l elementof z, determine (g? f) ((4k,