CPU PERFORMANCE CALCULATION - I NEED HELP

Due to the RAM capacity, if a computer system can run two programs with the same feature only, and these processes require 80% of their time waiting for entry / exit.

How long is the CPU idle (the CPU waits idle without doing anything)?

New memory has been added to the computer. Now, a total of 4 programs with the same feature can be run on the computer. Calculate the performance of the CPU.

thanks.