Suppose a farmer has three kinds of land for growing peaches; good $-$ better $-$ and best. As the farmer increases production $-$ she will use the best land first $-$ and costs will be low. At some point $-$ she will run out of the best land and will have to start using the better land $-$ and costs will be a little higher. This describes the:

law of demand.

law of diminishing marginal costs.

law of increasing opportunity cost.

law of marginal analysis.