Joe sold gold coins for $2,500 that he bought a year ago for $2,500. He says, "At least I didn't lose any money on my financial investment." His economist friend points out that in fact he did lose money, because he could have received a 1 percent return on the $2,500 if he had bought a bank certificate of deposit instead of the coins. The economist's analysis in this case incorporates the idea of:
1) marginal benefits that exceed marginal costs
2) opportunity costs
3) imperfect information
4) normative economics