$4.)$ Assume that we have an $8,000-$square$-$foot metal storage building valued at $$1$ million with contents valued at $$500,000.$ We decide to install a fire sprinkler system for this building. The building's property insurance premium without fire sprinklers is $$19,900$ per year. If we install fire sprinklers, the property insurance premium drops to $$5,274$ per year. Assume for this type of building and its storage$-$use occupancy that a fixed fire sprinkler system here will cost $$\frac{6\mathrm{.}30}{?}$ square foot. What is the payback period $($in years$/$months$)$ as measured on property insurance savings for adding fire sprinklers?