Smith Mfg$.,$ produces various goods and has a limited number of machining hours available. The following data apply to Product AJ$405$:

Sales price per unit: $$9\mathrm{.}60$

Variable cost per unit: $$6\mathrm{.}20$

Machine time per unit: $4$ hours

Management is deciding whether to limit the production of Product AJ$405$ or focus on other products. Which of the following amounts should management focus on when making their decision?

a$.$ $$0\mathrm{.}85.$

b$.$ $$2\mathrm{.}40.$

c$.$ $$3\mathrm{.}40.$

d$.$ $$6\mathrm{.}20.$