You work on a consulting project where your task is to investigate whether publicly traded and privately held firms have different cost structures. You collect data on production output and its costs for both types of firms and estimate the following regression model: y = Bo + B1Pub + B2output + B3(Pub * output) + e. In this model, y is cost measured in dollars, output is the number of units produced and Pub is a dummy variable that equals 1 if a firm is publicly traded, and 0 if it is privately held. After running this regression, you find that, on average, publicly traded firms have greater fixed costs than privately held firms (recall that fixed costs do not depend on the level of output). Furthermore, you find that, on average, publicly traded firms have lower variable (or per unit) cost than privately held firms. These findings imply that: