Carla Vista Industries incurs unit costs of $$7($$$4$ variable and $$3$ fixed$)$ in making an assembly part for its finished product. A supplier offers to make $16,800$ of the assembly part at $$5$ per unit. If the offer is accepted, Carla Vista will save all variable costs but no fixed costs. Prepare an analysis showing the total cost saving, if any, that Carla Vista will realize by buying the part. $($Enter negative amounts using either a negative sign preceding the number e$.$g$.-45$ or parentheses e$.$g$.(45).)$