manny, a calendar-year taxpayer, uses the cash method of accounting for his sole proprietorship. in late December he performed $16000 of legal services for a client. manny typically requires his clients to pay his bills immediately upon receipt. assume Mandy's marginal tax rate is 37 percent this year, and that he can earn an after-tax rate return of 8 percent on his investments. what is the after- tax income if manny sends the bill in December? what is the after-tax income if manny sends his client the bill in January? use exhibit 3.1