In order to come within the scope of the truth in lending act, a loan must be in the amount of unless it is secured by a mortgage on real estate.

A loan must be in the amount of $25,000 or less unless it is secured by a mortgage on real estate in order to come within the scope of the Truth-in-Lending Act,

To add, the Truth in Lending Act (TILA) of 1968 is United States federal law designed to promote the informed use of consumer credit.

a. the cost of reducing it's existing pollution by one unit.

Explanation:

Marginal cost refers to the addition to total cost when one more unit of output is produced. Marginal cost in the given case would refer to the additional cost incurred for reducing the current pollution level by one unit.

In the given case, a firm is charged $250 for each unit of pollution emitted under the pollution tax option.

It is also stated that all the firms experience increasing marginal costs of pollution reduction.

This means, as additional units of pollution are reduced, the additional costs would go on increasing.

If a firm finds that, reducing 1 unit of pollution from the current level costs it equal or more than $250, it will opt to pay $250 since, for each subsequent unit of pollution reduction, the additional costs would rise.