Given R$($I$,$ N$,$ C$,$ S$)$ and F $\{$I$->$N$,$ I$->$C$,$ I$->$S$,$ C$->$S$\}$

$-$ Calculate the closure of all possible subsets of attributes

Hint: how many subsets a set has? Ignore the empty set.

$-$ dentify all super keys

$-$ Identify all candidate keys