Hours of operation Marginal cost 1 4 2 8 3 12 4 16 5 20 6 24 7 28 45) Julianne runs a business and needs to decide how many hours to stay open. Table 2.2 illustrates her marginal costs of staying open for each additional hour. Suppose that Julianne's marginal benefit of staying open per hour is $24. If she is following the marginal principle, how many hours should Julianne stay open?