In relational databases using closure do the following example

R = (A, B, C, G, H, I)

F = {A B A C CG H CG I B H}

(AG)+

1. result = AG

2. result = ABCG (A C and A B)

3. result = ABCGH (CG H and CG AGBC)

4. result = ABCGHI (CG I and CG AGBCH)

Is AG a candidate key?

1.Is AG a super key?

1.Does AG R? == Is (AG)+ R

2.Is any subset of AG a superkey?

1.Does A R? == Is (A)+ R

Does G R? == Is (G)+ R