Which of the following would reduce a firm's WACC after tax? a. A firm invests in an average-risk project using equity, rather than debt financing. b. A supermarket chain decides to establish hardware stores which increases its systematic risk. c. A firm issues bonds and uses the proceeds to repurchase stock. d. A firm issues shares and uses the proceeds to pay off a bank loan. e. A firm significantly improves its operating cost control to boost profits.