Which of the following would reduce a firm's WACC before tax? a O a. A pharmaceutical research company develops a 100% effective COVID vaccine, which reduces its systematic risk in the market. O b. A firm issues shares and uses the proceeds to pay off a bank loan. Oc. A firm invests in an average-risk project using debt, rather than equity financing. O d. A firm issues bonds and uses the proceeds to repurchase stock. e. A supermarket chain decides to establish hardware stores which increases its sensitivity to market fluctuations