Mining rare-earth minerals would be a rational economic policy if and only if: The benefits of mining are greater than the opportunity cost of mining. The opportunity cost of mining is zero. The direct and opportunity cost of mining is lower than- or equal to - the economic benefits of mining. The benefits of mining, in the form of a new comparative advantage in rare-earth minerals, are greater than the cost of mining, including damage to the environment, regardless of the opportunity cost. B and D only