Answer:
a). lower, higher
b). lower, lower
Explanation:
The abatement costs may be defined as the cost that is borne by a firm or an organization when it is necessary to remove any undesirable nuisances or any negative byproducts of the process that is created during the production process. It is cost incurred in eliminating a negative externality such as environmental externality like pollution.
In the context, for solving the pollution abatement cost, the tradeable emissions permits as they are tradebale, an organization with a lower abatement cost sells the permits to the higher abatement cost firms.
Even after selling, the firm still have to reduce the pollution output, then the firm that sold the permit would have lower abatement cost and the negative externality is also reduced at the lower possible cost.