John, a calendar year taxpayer, uses the cash method of accounting for his small business. On December 6, 2016 he receives a $20,000 legal bill for services rendered by his lawyer. He can pay the legal bill in 2016 or next year in 2017. Assuming a marginal tax rate of 30% in both 2016 and 2017, and a 7% rate of return, in which year, 2016 or 2017, should John pay the legal bill? Show how you arrived at the answer.