Explain whether each of the following would be expensed on the income statement in 2004 or in some later year, and why.

a. Inventory purchased in 2004 but sold in 2005.

b. Estimated warranty costs for goods sold in 2004; the warranty servicing will take place in 2005 and 2006.

c. Bad debts caused by 2004 sales; the actual bad receivables will not be identified until a later year.

d. Research and development costs incurred in 2004 but aimed at producing a better product in later years.