Suppose that three processes, $P1,P2$ and P $3,$ are running in a multiprogramming environment.

P$1$ executes for $10$ units of time, waits on I$/$O for $10$ units of time, and then processes for another $10$ units.

P$2$ executes for $5$ units of time, waits on I$/$O for $10$ units of time, and then processes for $3$ units of time.

P$3$ executes for $5$ units of time, waits.on I$/$O for $5$ units of time, and then processes for $10$ units of time.

What is the minimum amount of time needed to complete the processing of all the processes?