Arcon Computer builds high$-$end custom PCs$.$ There are four main steps in building computers. These steps are:

Step $1$: After receiving an order, a technician picks up the parts from the warehouse. This process takes anywhere between $10$ minutes to $20$ minutes $($everything is equally likely$)$

Step $2$: Parts are carefully mounted to the case with proper cable management. This process takes at least $60$ minutes, at most $110$ minutes, and most likely $80$ minutes.

Step $3$: After assembly, the technician installs the operating system and other related software. The installation process follows a normal distribution with a mean of $50$ minutes and a standard deviation of $5$ minutes.

Step $4$: The technician runs several benchmarks on the computer. If necessary, the technician fixes any issue arises. The table below presents the number of issues, the probability of occurrence, and time $($in minutes$)$ it takes to complete the step.