*4.8 Suppose that the inverse demand function for paper is p = 300 - 2Q, and the marginal external harm from emissions is MCp = 60 + Q, and the marginal external harm from emissions is MCx = Q. Determine the unregulated competitive equilibrium and the social optimum (where total surplus is maximized).

What specific tax (per unit of output) would achieve the social optimum? (Hint: See Q&A 16.2.)