Four processes execute on a system with a single CPU and a single I$/$O device. The system uses multiprogramming without time$-$sharing. Each process has a compute$-$bound phase of $10$ time units followed by an $1/$O$-$bound phase of $20$ units. A process cannot initiate the I$/$O phase until the I$/$O device becomes free.

The processes start executing in the order p$1,$ p$2,$ p$3,$ p$4.$

During the execution of all processes,

the CPU is idle for $$ time units

the I$/$O device is idle for $$ time units