Given two DFAs, A and D, show that you can construct a DFA C such that L(C) = phi if and only if L(A) L(B). Prove that your construction works by proving the if and only if statement. Use the result of the previous question to show that the following language is decidable. Just give the construction (step 1 in the lecture slides), as you have done the bulk of the correctness proof (step 2 in the lecture slides) in the previous question. L = {(R, S)}|R and S are regular expressions and L(R) L(S)}