$($a$)$ Multiply $-21($negative$)$ with $+63$ in an $12-$bit representation using the shift$-$and$-$add technique.

Show the steps.

$($b$)$ Briefly describe the IEEE $754$ scheme of representing Iloating$-$point numbers.

$($c$)$ What are the smallest and the largest lloating$-$point numbers represented using a $24-$bit signed

mantissa and an $8-$bit excess$-128$ signed exponent scheme?