Consider the relation scheme R = {A, B, C, D} with functional dependencies A rightarrow C and B rightarrow D. What is the only key? (You must do this problem without using closure directly. Describe your reasoning clearly). Given R (A, B, C, D, E), with functional dependencies AB rightarrow D, AC rightarrow E, BC rightarrow D, D rightarrow A, and E rightarrow B. We want project those FD's onto relation S(A, B, C). Give the FD's that hold in S. (Number each FD that holds in S. Each relation should be shown in the form R#(W, X, Y, Z). Describe your reasoning clearly)