Answer:
$380
Step-by-step explanation:
Firm A Firm B Firm C
1st unit of pollution $20 $50 $500
2nd unit of pollution $60 $100 $700
3rd unit of pollution $120 $180 $1,000
4th unit of pollution $200 $350 $1,500
5th unit of pollution $300 $500 $2,500
6th unit of pollution $400 $600 $4,000
Firm A's cost of eliminating four units of production = the sum of the costs of eliminating the four units = $20 (for the first unit) + $60 (for the second unit) + $120 (for the third unit) + $200 (for the fourth unit) = $380
This table does not show cumulative costs, instead it shows the marginal costs of eliminating an extra unit of pollution.