The facility includes a $1\mathrm{.}5-$mile track, $60$ pitstop work stations each with a covered shop$/$work area, piped in pressurized air, deep sinks with running water and cleaning solvent, $110/220$ electrical service, and benches for working on$,$ tuning up$,$ changing engines and tires, etc. on the Go$-$Karts. Fixed Operating Costs are as follows: Depreciation on the facilities $$3,600$ per year. Real estate taxes $$1,200$ per year. Utilities average $$320$ per month. General track and facility maintenance averages $$105$ per month. Chuck$$s son is employed to operate and maintain the facilities at an annual salary of $$27,600.$ Variable Operating Costs are as follows: Engineering students from Monterrey Peninsula College work as interns. One engineering student can be assigned to as many as $6$ pitstop workstations to trouble shoot and provide ideas regarding sprocket ratios, engine issues, track temperature$/$tire pressure, etc. As an intern, they are paid $$21$ per work station per day. The pitstop work stations rent for $$35$ per Go$-$Kart owner per day. Instructions $($a$)$ Determine the annual number of pitstop work station rentals and revenue Chuck needs to break even using the contribution margin technique. $($b$)$ If the current annual number of pitstop workstation rentals is $6,915,$ calculate the $$margin of safety$.$