Answer: if the marginal benefit of the movie exceeds its marginal cost.
Explanation: Marginal benefit refers to the benefit a consumer gets by consuming one additional unit of a good or service. Similarly, the cost of producing or acquiring one additional unit of any good or service is called marginal cost.
The difference between marginal cost and marginal benefit is the utility benefit received by a consumer. Thus, in order to watch a movie the marginal benefit from watching a movie must exceed its marginal cost.