Suppose an electricity distribution firm purchases a number of metal poles for inventory at a price of per pole. Sometime later, metal poles become obsolete in the industry in favour of fiberglass poles, and command a price of per pole in the scrap metal market. By the time the firm switches to fiberglass poles, some of the metal poles previously purchased remain in the firms inventory. The price of a fiberglass pole is . Assume that 0 < < < . In terms of these variables, quantify the accounting and economic costs of each of the following activities:

i. Past purchase of a metal pole for inventory.

ii. Current purchase of a fiberglass pole for inventory.

iii. Keeping a fiberglass pole in inventory.

iv. Keeping a metal pole in inventory.

v. Selling an uninstalled metal pole for scrap.

Briefly explain which of the quantified costs are sunk