Which of the following statements is least accurate?

a. Only debt has an after-tax cost adjustment (1-T) because only interest expense is tax deductible.

b. The cost of newly issued common stock exceeds the cost of retained earnings because issuing new common stock may send a negative signal to the capital markets, which may depress the stock price.

c. The cost of retained earnings exceeds the cost of newly issued common stock because the firm has to pay flotation costs to the underwriter.

d. The cost of preferred stock is often less than the cost of debt because corporations can exclude 50% of preferred dividends from taxation.