$(20$ points$)[$Instruction Mix and CPI$]$ Assume that for a given program, $65\%$ of the executed

instructions are ALU, $25\%$ are load$/$store$,$ and $10\%$ are branch.

a$)$ Given this instruction mix and the assumption that an ALU instruction requires $2$ cycles,

a load$/$store instruction takes $7$ cycles, and a branch instruction takes $3$ cycles, find the

effective CPI.

b$)$ For a $20\%$ improvement in performance, how many cycles, on average, will an ALU

instruction take if load$/$store and branch instructions are not improved at all?