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 make , save $6.00 per unit buy , save $ 16.00