Isabel, a calendar-year taxpayer, uses the cash method of accounting for her sole proprietorship. In late December she received a $20.000 bill from her accountant for consulting services related to her smali business. Isabel can pay the $20.000 bill anytime before January 30 of next year without penalty. Assume her marginal tax rate is 37 percent this year and next year, and that she can earn an afterstax rate of return of 12 percent on her investments. Recuired: a. What is the after-tax cost if tsabel pays the $20,000 bill in December? b. What is the after-tax cost if Isabel pays the $20,000 bill in January? Use Exhibit 3.1. Note: Round your answer to the nearest whole dollar amount. c. Based on requirements a and b, should Isabel pay the $20.000 bill in December of January? Complete this question by entering your answers in the tabs below. What is the after-tax cost if tsabel pays the $20,000 bill in December? EXHIBIT 3-1 Present Value of a Single Payment at, Various Annual Rates of