If a firm spends $400 to produce 20 units of output and spends $880 to produce 40 units, then between 20 and 40 units of output, the marginal cost of production is:

The common stock and debt of northern sludge are valued at $65 million and $35 million, respectively. investors currently require a return of 15.9% on the common stock and a return of 7.8% on the debt. if northern sludge issues an additional $14 million of common stock and uses this money to retire debt, what happens to the expected return on the stock? assume that the change in capital structure does not affect the interest rate on northern’s debt and that there are no taxes.