Short Answer Questions 11-8 thru to 11-12 and Exercise 11-13.
11-8 There is an opportunity cost in holding inventory for a time period as the money used to make the purchase could be otherwise invested in short term with a return. The actual dollars spent would be less with the lower unit costs, in the long run, but the volume purchased as a requirement for eligibility for a discount means that a large sum of money is being underutilized (in terms of opportunity costs) when compared to the option of purchasing smaller increments of inventory.
11-9) If the operating income is negative then the money made from investments or from loans receivables and interest receivables should be taken into consideration. If these other types of income balance off the loss and bring the overall income into the black then the company can still run, but eventually the financing and investments aspects of the company should feed the operations side and bring the operations income into the positives. (If desired) This negative operating income could mean that a company is in a transition phase or a building/expansion phase wherein their operations has yet to catch up with their expansion undergone.

11-10) I would say that depreciation should be considered relevant as the depreciation expense decreases taxable income and therefore increases overall net income. This fact would mean that through analysis a company could effectively purchase equipment with a high depreciation rate to decrease their taxes paid in a future year. However the original cost of the equipment is irrelevant as these costs will not affect future decisions.
11-11) In most cases but not in all cases. If the short-run profit is greater in situation A but the long-run potential suffers, (because of this decision to optimize short-term gains), then decision B may be elected if the long-term potential is