A negative externality problem

I'm teaching sophomore level environmental and resource economics (with no prerequisite). We just finished covering the principles level negative externality market model. Here is the problem set:

Consider the following model:

1. Qd=200-20P
2. Qs=20P
3. MEC=2
4. MSC=MPC+MEC

 

1. At the unregulated (inefficient) private market equilibrium :
   1. What is the consumer surplus?
   2. What is the producer surplus?
   3. What is the external cost?
   4. What are the net benefits?
2. Consider the regulated (efficient) social market equilibrium
   1. What is the consumer surplus?
   2. What is the producer surplus?
   3. What is the external cost?
   4. What are the net benefits?
3. What is the change in net benefits realized moving from the inefficient equilibrium to the efficient equilibrium?

Note that the regulation is a quantity restriction. We're saving taxes for the marginal damage-marginal abatement cost model.

Any suggestions?