Q$7.$ Consider the relation $R=\{A,B,C,D,E,F,G,H,$I,$J,K,L,M,N\}$ and the functional dependencies

L$\}\}.$

$($a$)(2\%)$ What is the key for $R?$

$($b$)(6\%)$ Decompose $R$ into $2NF,$ then $3NF$ relations.