4) (Exercise 4.5 in Phaneuf and Requate) Consider a situation where the marginal damage function is known and equal to D'(E) = d . E. The aggregate marginal abatement cost curve is given by -C'(E) = a - bE where a is a random variable uniformly distributed on the [a, a]. The regulator wants to apply the hybrid instrument with a supply of traditional tradable permits, a tax rate as an upper valve, and a subsidy rate for nonused permits (