Consider the following relations and for each determine the candidate key(s) and in which normal form the relation is (relation can be in multiple normal forms). Please consider the following normal forms: 1NF, 2NF, 3NF and BCNF.
a) R(A, B, C, D) and functional dependencies are B→C, D→A
b) R(A, B, C, D) and the Functional Dependencies are A→B, C→BD, B→C
c) R(A, B, C, D) and the Functional Dependencies are A→B, C→BD, B→C
d) R(A, B, C, D, E) and the Functional Dependencies are A→BC, B→AD, C→A, C→→ E