QUESTION $20$

Consider a $4-$bit carry$-$lookahead adder. Identify the number of transistors and gate$-$delays for $c2,$ which is the carry$-$out for digit $2.$ Hint: $g=ab,p=a+b,$ and the expression for each digit's carry$-$out is $co=ab+(a+b)ci=g+p*ci.$

a$.26$ transistors and $2$ gate$-$delays

b$.13$ transistors and $2$ gate$-$delays

c$.4$ transistors and $4$ gate$-$delays

d$.10$ transistors and $4$ gate$-$delays