Figure $5\mathrm{.}8$ shows a $4-$input AND gate built using a tree $($a$)$ and a chain $($b$)$ of gates.

Determine the activity factors at each node in the circuit assuming the input probabilities PA $=$ PB $=$ PC $=$ PD $=0\mathrm{.}5.$

SOLUTION: Figure $5\mathrm{.}9$ labels the signal probabilities and the activity factors at each node

based on Table $5\mathrm{.}1$ and EQ $(5\mathrm{.}14).$ The chain has a lower activity factor at the intermediate nodes.