Final answer:
The relevant cost for deciding whether to build a retail store or sell the land is the current offer of $8 million, as the original purchase price is a sunk cost and not relevant for future decisions. The decision should consider potential retail store profits versus the sale offer.
Step-by-step explanation:
In the scenario you provided, the relevant cost for the decision as to whether or not you should build a new retail store is $8 million. This is the highest price that your business would be able to get for the land currently. The original purchase price of $20 million is a sunk cost, meaning it has already occurred and cannot be changed; therefore, it is irrelevant for future decision-making. When assessing whether to build the retail store or sell the land, your business should consider the potential profit from the retail operation versus the current sale offer of $8 million.
It's also important to consider the example given where a center earns revenues of $20,000 and has variable costs of $15,000. In this case, the center should continue in business as it's covering its variable costs and contributing towards fixed costs and possibly making a profit.