A manufacturing facility needs the raw material $($A$,$ B$,$ C and D$)$ to undergo two processes, grinding and deburring. The estimated job time required $($in hours$)$ are detailed below. The Grinding should be finished before Deburring. Each shop has dedicated workers. Assuming that these are the only jobs in hand at the facility. Using Johnson's rule find the order in which the job should be carried out to minimize the make$-$span.