$4.$ Sales of $50,000$ units at $$4\mathrm{.}00$ per unit are made monthly. The unit cost is $$1\mathrm{.}50.$ Incremental cost of $$1\mathrm{.}00$ per unit to further process the units will result in the $50,000$ units being sold for $$4\mathrm{.}75$ each. The company should:

a$.$ Do further processing and sell the units at $$4\mathrm{.}75$

b$.$ Sell the units at the current stage of completion $(50,000$ at $$4)$

c$.$ Do further processing on only $1/2$ of the units

d$.$ Commit its resources to a different product