Company manufactures a part for its production cycle. The costs per unit for 5,000 units of he part are as follows: Direct materials Direct labor Variable factory overhead Fixed factory overhead Total costs $3.00 5.00 4.00 4.00 $16.00 The fixed factory overhead costs are unavoidable. Spalding Company has offered to sell 5,000 units of the same part to Birch Company for $15 per unit. Assuming no other use for the facilities, Birch Company should A) buy the part from Spalding Company to save $1 per unit B) buy the part from Spalding Company to save $3 per unit C) make the part to save $1 per unit D) make the part to save $3 per unit