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 $40$ time units followed by an I$/$O$-$bound phase of $80$ 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$4.$