the texas ring company has offered to sell northern ring company 5,000 telephones for $20 per unit. if northern ring company accepts the offer, $8,000 of fixed overhead will be eliminated. northern ring should: a. make the telephones; the savings is $10,000 b. buy the telephones; the savings is $8,000 c. buy the telephones; the savings is $10,000 d. make the telephones; the savings is $12,000