Based on the corporate valuation model, Wang Inc.'s total corporate value is $720 million. Its balance sheet shows $50 million notes payable, $100 million of long-term debt, $40 million of common stock (par plus paid-in-capital), and $160 million of retained earnings. What is the best estimate for the firm's value of equity (in millions)? a. $670 million b. $570 million c. $620 million d. $560 million e. $610 million