Suppose there is a simple index of two stocks, stock A and stock B. Stock A opens on Monday with 10,000 shares at $5.50 per share. Stock B opens on Monday with 8000 shares at $6.25 per share. Stock A opens on Tuesday at $5.80 per share, and stock B opens on Tuesday at $6.65 per share. Both stocks have the same number of shares that they opened with on Monday. What is the rate of change of this simple index over 1 day? A. 5.9% B. -5.6% C. 5.6% D. -5.9%