Parks Corporation currently manufactures 3,000 staplers annually for its main product. The costs per stapler are as follows: Direct materials $ 3 Direct labor 7 Variable overhead 4 Fixed overhead 7 Total $ 21 Gallup Company has contacted Parks with an offer to sell it 3,000 staplers for $18 each. $5 of the fixed overhead per unit is unavoidable. Prepare an incremental analysis for the make-or-buy decision. (Enter negative amounts using either a negative sign preceding the number e. g.-45 or parentheses e. g.(45)