$3$A$)$ Design a code converter to convert a decimal digit represented in $84-2-1$ code to a decimal digit

represented in gray code using $3$:$8$ decoders and minimum external gates.

$3$B$)$ Design a $16$:$1$ MUX using $2$: $1$ MUXs ONLY.

$3$C$)$ Using asynchronous hexadecimal counter ICs and external gates, design a $2-$ digit hexadecimal

counter which counts from $00$ to $89H$ and repeats.