Christopher is a cash-method, calendar year taxpayer, and he made the following cash payments related to his business this year. Calculate the aftertax cost of each payment assuming Christopher has a 37 percent  marginal tax rate.

a. $500 fine for speeding while traveling to a client meeting.
b. $800 of interest on a short-term loan incurred in September and repaid in November. Half of the loan proceeds were used immediately to pay salaries and the other half was invested in municipal bonds until November. 

c. $600 for office supplies in May of this year. He used half of the supplies this year and he will use the remaining half by February of next year.
d. $450 for several pairs of work boots. Christopher expects to use the boots about 80 percent of the time in his business and the remainder of the time for hiking. Consider the boots to be a form of clothing.