Urgent help please!! Assume we have three relations $R(A,B),S(B,C)$ and $Z(C).$ All three attributes $,$ and $C)$ are integer tes

Relation $R(A,B)$ contains the following tuples: $(1,2),(2,3),(3,2),(4,1),(5,8)$ and $(6,4).$

O Relation $S(B,C)$ contains the following tuples $(1,1),(1,2),(2,1),(2,3),(4,1),(4,2),(4,3)$ and $(5,1).$

O Relation $Z(C)$ contains the following tuples $(1),(2)$

nat a key is a minimal superkey, and that a key is not a superkey

$($a$)$ Give an example of an attribute that cannot be a key for relation in $S$

$($b$)$ Write the number of the results of the relational expression: $RxS?$

$($c$)$ Write the results for the following relational algebra expression: $|)><mi\; id="EditorElement\_49075">|</mi><mi\; id="EditorElement\_49066">|</mi><mi\; id="EditorElement\_49067">(</mi><mi\; id="EditorElement\_49060">R</mi><mi\; id="EditorElement\_48984">|</mi>$

$($d$)$ Write the results for the following relational algebra expression: ${}_B(S)$

$($e$)$ Write the results for the following relational algebra expression: ${}_A>2(R)$

h$)$ Write the results for the following relational algebra expression: $SZ$

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