Let A, B two sets such that A ⊂ B and A 6= B. Define the function f : A → B given by f = {(x, x) : x ∈ A}. (a) Write a mathematical sentence expressing the statement that "f is injective". Make it as precise as possible using all the information you have at hand. (b) Is f injective ? prove or disprove. (c) Write a mathematical sentence expressing the statement that "f is surjective". Make it as precise as possible using all the information you have at hand. (b) Is f surjective ? prove or disprove. g