On December 30, 2015, 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 2017, after Charles had paid $60,000 on the principal of the note, he received an offer to sell the land for $500,000 cash. What advice can you provide Charles that will minimize the present value of the tax liability for Maud and him?