You are trying to decide whether to trade in your ink-jet printer for a more recent model. Your usage pattern will remain unchanged, but the old and new printers use different ink cartridges. Are the following items relevant or irrelevant to your decision?
a. The price of the new printer
b. The price you paid for the old printer
c. The trade-in value of the old printer
d. Paper costs
e. The difference between the cost of ink cartridges