Sunland Inc. has been manufacturing its own shades for its table lamps. The company is currently operating at $100\%$ of capacity, and variable manufacturing overhead is charged to production at the rate of $40\%$ of direct labour costs. The direct materials and direct labour costs per unit to make the lampshades are $$4\mathrm{.}70$ and $$6\mathrm{.}00,$ respectively. Normal production is $48,400$ table lamps per year.

A supplier offers to make the lampshades at a price of $$13\mathrm{.}80$ per unit. If Sunland Inc. accepts the supplier's offer, all variable manufacturing costs will be eliminated, but the $$46,800$ of fixed manufacturing overhead currently being charged to the lampshades will have to be absorbed by other products.

$($a$)$

Prepare the incremental analysis for the decision to make or buy the lampshades.