1) Given the relation R and the following functional dependencies, answer the following questions. R(A,B,C,D,E,F) Note : All attributes contain only atomic values.) FD1: A BCD FD2: BC-) DE FD3: B->D FD4:DA a Use Armstrong Axioms (and additional rules taught in the class) and compute attribute closure for each single attribute of R. Mention which rule you have used at each step. b) Briefly explain what is the candidate key and prove that AF is a candidate key. Mention the rules that you use. c Can AF also be a primary key? Yes/No? Explain d) Can AFB be a primary key? Yes/No? Explain why. If No, mention what type of key it is