5. (3 points) A livestock farm currently emits 10,000 gallons of toxic sewage into a nearby river. The following table shows the total costs (TC) in dollars of cleaning up the toxic sewage to different levels, together with the total benefits (TB) in dollars of doing so. TC MC N/A MB N/A Sewage level 10,000 7,500 5,000 2,500 Current 4,000 10,000 18,000 28,000 TB Current 50,000 95,000 135,000 170,000 a. Using the information in the table calculate the marginal costs (MC) and marginal benefits (MB) of reducing sewage emissions for this city. b. What is the optimal level of toxic sewage emissions for this farm