A donor made his first taxable gift in 1979 and his second taxable gift in the current year. In the intervening years, the highest gift tax rates declined. In calculating the tax on taxable gifts of previous periods, which rate schedule is applicable: the one for the year in which the donor made the earlier gift or the one for the current period?

a. The donor must compare taxable gifts of previous periods against current period gifts and depending on which year is lower determines the rate schedule used.

b. The rate schedule for the current period is used to determine the tax on taxable gifts of previous periods.

c. The donor must compare taxable gifts of previous periods against current period gifts and depending on which year is higher determines the rate schedule used.

d. The rate schedule for the year in which the donor made the earlier gift is used to determine the tax on taxable gifts of the earlier periods.