Consider a four$-$step serial process with processing times given in the following list. There is one machine at each step of the process, and this is a machine$-$paced process.

Step $1$: $31$ minutes per unit

Step $2$: $25$ minutes per unit

Step $3$: $34$ minutes per unit

Step $4$: $14$ minutes per unit

Assuming that the process starts out empty, how long will it take $($in hours$)$ to complete a batch of units?