SE21-4. Refries Refrigerator Company manufactures ice-makers for installation in refrigerators. The costs per unit for 20,000 units of ice-makers, are as follows: LOS $ 7 Direct materials. ....... Direct labor.......... Variable overhead ...... Fixed overhead............ Total costs ............ Cool Compartments Inc. has offered to sell 20,000 ice-makers to Refrigerator Company for $28 per unit. If Refrigerator accepts Cool Compartments'offer, the facilities used to manufacture ice-makers could be used to produce water filtration units. Revenues from the sale of water filtration units are estimated at $80,000, with variable costs amounting to 60% of sales. In addition, $6 per unit of the fixed overhead associated with the manufacture of ice-makers could be eliminated. For Refrigerator Company to determine the most appropriate action to take in this situation, the total relevant costs of make vs. buy, respectively, are a $600,000 vs. $560,000. b. $648,000 vs. $528,000. c. $600,000 vs. $528,000. d. $680,000 vs. $440,000