Audio Labs collected the following information on the cost of producing 20,000 speaker units: Direct materials $32.00 per unit Direct labour 4.00 per unit Variable overhead 16.00 per unit Fixed overhead 20.00 per unit Cartunes has offered to sell Audio 10,000 speakers for $56.00 each. Should Audio Labs make or buy the parts if the facilities remain idle when speakers are purchased? make, save $4.00 per unit buy, save $16.00 per unit buy, save $4.00 per unit make, save $2.00 per unit make, save $6.00 per unit