Confusing math problem

Question

A company manufactures small refrigerators. The total cost to manufacture 77 refrigerators is $10275. The total costs to manufacture 105 refrigerators is $13775. Assume that total cost, C, is linearly related to the number of refrigerators, x, the company manufactures and includes a fixed cost and a cost per refrigerator.

A)  Write the equation for 

 in terms of 

, the number of refrigerators manufactured. 

B) The total cost to manufacture 223 refrigerators is 

C) The fixed costs are $

Answer 1

28 cost 13775 - 10275 = 3500

105-77 = 28

each cost 3500/28 = $125 average variable cost, per unit output

10275-77(125) = $650 fixed cost

C = 125x +650

C(223) = 125(223) +650 = $28,525