Suppose there is a simple index of two stocks stock A and stock B. Stock A opens on Monday with 7500 shares at $4.75 per share. Stock B opens on Monday with 2500 shares at $8.95 per share. Stock A opens on Tuesday at $4.50 per share, and stock B opens on Tuesday at $8.15 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?