Given The Relation S A1 A2 A3 A4 A5 With The Following Dependencies A5 A1 A2 A2

Given the Relation S = {A1, A2, A3, A4, A5} with the following dependencies:

{A5,A1} > {A2}

{A2,A3} > {A4}

{A3,A4} > {A1}

a.      Define the term Candidate key.

b.      Is {A5,A1} a candidate key of R? Explain

c.      Is {Z5,Z1,Z3} a candidate key of R? Explain

d. Explain why {Z1,Z2,Z3,Z5} is a superkey of R but not a key of R.