With regard to the weighted average cost of capital (WACC) for a firm, a) the book value weights of capital are the preferred choice for use in calculating the WACC for a firm. b) historical or embedded costs of capital should be used in lieu of marginal costs. c) the WACC must be risk-adjusted when applied to projects that are more risky or less than the firm overall or the average project of the firm. d) the WACC is not affected by dividend policy of the firm. e) the WACC formula includes an adjustment for taxes (1-t) because the dividend payments on common stock are tax deductible