Answer:
b. marginal cost of those 50 records is $80,000.
Explanation:
The computation is shown below:
The average cost of selling 1,200 records is
= $1,200,000 ÷ 1,200
= $1,000
Now
The average total cost of selling 1,250 records is
= $1,280,000 ÷ 1,250
= $1,024
Now for the extra 50 records, the marginal cost is
= $1,280,000 - $1,200,000
= $80,000
Hence, the correct option is b.