Manny, a calendar-year taxpayer, uses the cash method of accounting for his sole proprietorship. In late December he performed $23,000 of legal services for a client. Manny typically requires his clients to pay his bills immediately upon receipt. Assume Manny's marginal tax rate is 37 percent this year and next year, and that he can earn an after-tax rate of return of 6 percent on his investments. Required: a. What is the after-tax income if Manny sends his client the bill in December? b. What is the after-tax income if Manny sends his client the bill in January? Use Exhibit 3.1.