Plant Nutrients, Inc. (PNI) sells fertilizers and pesticides to various retail hardware and nursery stores on terms of "2/10, net 30." The company currently does not grant credit to retailers with a 3 (fair) or 4 (limited) Dun & Bradstreet Composite Credit Appraisal. An estimated $5,475,000 in additional sales per year could be generated if PNI extended credit to retailers in the "fair" category. The estimated average collection period for these customers is 75 days, and the expected bad-debt loss ratio is 5 percent. The company also estimates that an additional inventory investment of $800,000 is required for the anticipated sales increase. Approximately 10 percent of these customers are expected to take the cash discount. PNI's variable cost ratio is 0.75, and its required pretax rate of return on investments in current assets is 18 percent. Determine the following:

a. Marginal profitability of additional sales

b. Cost of additional investment in receivables

c. Additional bad-debt loss

d. Cost of additional investment in inventory

e. Additional cash discounts

f. Net change in pretax profits.