In the short run, a firm's marginal cost often increases as output rises because some inputs are fixed. To increase production, a firm might need to intensify its operations, such as by running extra shifts or reallocating resources from other product lines, leading to higher marginal costs. These factors can include equipment strain, worker fatigue, overtime wages, and higher energy consumption. For example, a bakery might incur higher costs for each additional loaf by operating overnight or shifting production away from other baked goods.