Which of the following is NOT correct regarding a firm's WACC?

It is the overall return the firm must earn on its existing assets to maintain the value of its stock.

It is the discount rate that should be applied to a proposed investment's future cash flows if the proposed investment is similar to the firm's existing activities.

It should include the firm's after-tax cost of debt.

It reflects the risk and the capital structure of the firm's existing assets as a whole.

It should be used to evaluate all projects regardless of project risk.