Should the WACC be higher for a $250mm or $3B market cap company?

Let’s think about the components of the WACC: CoE, E / (E + D), CoD, D / (E + D). Now, we know that the CoE will be higher for the $250mm company, and that’s a portion of the WACC but not the entire thing. So, you should ask the interviewer if the capital structure and CoD are the same for both companies. If the capital structure of both companies is the same, the smaller company would have the higher WACC by way of the higher CoE. If they aren’t the same, there would be no way to know which had a higher WACC.