21. A country is currently creating 40 tons of toxic waste per year. The table below shows the total costs and total benefits of reducing the amount of toxic waste to various amounts.

Total Tons	TC	MC	TB	MB
40 tons	Current	--	Current	--
30 tons	$50		$1000
20 tons	150		1500
10 tons	500		1850
0 tons	1200		2000

Calculate the marginal cost and marginal benefit of reducing toxic waste in 10 ton increments. What level of toxic waste should the country reduce to? Why?