emissions taxes vs. technology standards

Steel producers can choose among the following five production techniques. Suppose that the market price (and social cost) of ordinary inputs is 1 and that the social cost of each unit of SO2 emitted is 10.

Technique Per-unit input requirements

ordinary inputs (K) 28	emissions (SO2) 4	A
B	31	3
C	37	2
D	46	1
E	58	0

a. [3] Calculate the social cost of each technique. [Hint: social cost should reflect the cost of emissions as well as the production costs.] What production technique minimizes the social cost per unit of steel production? What is the amount of this social cost?