Decoders & Multiplexers

$1.)[20]$ Implement the following functions on a single $3-$to$-8$ decoder $(74$LS$138).$ Use minimal additional external logic gates. Remember that a $74$LS$138$ has active low outputs!

$F1(A,B,C)=$AB$+/$A$*/$B$*/$C

F$2($A$,$B$,$C$)=/$A$*$B $+$ A$*/$B