Four classes of instructions $($A$,$ B$,$ C$,$ and D$)$ have the following CPI for processors P$1$ and P$2$:

A certain program consists of $1$ million instructions divided into the following classes:

$($a$)$ Determine the CPU Time for each processor running this program.

$($b$)$ Based on your answer in $($a$),$ what is the average CPI for each implementation?