On December 30, 2021, Maud sold land to her son, Charles, for $50,000 cash and a 7% installment note for $350,000, payable over 10 years. Maud’s cost of the land was $150,000. In October 2023, after Charles had paid $60,000 on the principal of the note, he received an offer to sell the land for $500,000 cash. How can Charles minimize the present value of the tax liability for himself and Maud?