Joseph and Sandra, married taxpayers, took out a mortgage on their home for $350,000 in 1994. In May of 2019, when the home had a fair market value of $450,000 and they owed $220,000 on the mortgage, they took out a home equity loan for $100,000. They used the funds to purchase a single engine airplane to be used for recreational travel purposes. What is the maximum amount of debt on which they can deduct home equity interest? a. $50,000. b. $100,000. c. $220,000. d. $230,000. e. None of the above.