The Taxpayer Assistance Center (TAC) provides taxpayer assistance to help in the preparation of individual tax returns. The amount of assistance (A)

The Taxpayer Assistance Center (TAC) provides taxpayer assistance to help in the preparation of individual tax returns. The amount of assistance (A) that can be provided is a function of the number of professional accountants (P) and trained tax preparers (T) that are employed. The function given by:

A= 500P + 200T + 50PT. Calculate the marginal cost of providing additional assistance. Explain your answer