Computer $1($C$1),$ with a clock rate of $2$ GHz$,$ runs a program in $80$ seconds. Computer $2($C$2),$ with a clock rate of $4$ GHz$,$ runs the program in $20$ seconds. The number of instructions is the same for both computer $1($C$1)$ and computer $2($C$2).$

a$)$ What is the number of clock cycles executed by computer $2($C$2)?$

b$)$ If the average CPI for computer $1($C$1)$ is $8,$ what is the average CPI for computer $2($C$2)?$