The next three questions $(1-3)$ are based upon the following:

Great Southern Packing Company produces recyclable packing boxes. Currently, one production line produces $500$ boxes using five workers on an $8-$hour shift. Supposed that Great Southern Packing spends $$20$ per hour for each worker. The material cost is $$4\mathrm{.}5$ per box, and there is an overhead expense of $$500$ per $8-$hour shift.