In 2015, Sondra makes taxable gifts aggregating $300,000. Her only other taxable gifts amount to $200,000, all

Question:

In 2015, Sondra makes taxable gifts aggregating $300,000. Her only other taxable gifts amount to $200,000, all of which she made in 1997.
a. What is Sondra’s 2015 gift tax liability?
b. What is her 2015 gift tax liability under the assumption that she made the $200,000 of taxable gifts in 1974 instead of 1997?