When its variable costs are less than total revenue, a firm should shut down. ( )
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If there is a way to change a situation so that at least some people gain while no one in the economy loses, the situation is economically inefficient. ( )
The cross elasticity of demand for substitute goods must be less than zero. ( )
If the size of a tax increases, tax revenue will increase, and then decrease. ( )
A monopolistically competitive market is different from a monopoly market in that the former allows free entry and exit in the long run. ( )