Suppose there is a simple index of three stocks stock ABC stock XYZ and stock QRS Stock ABC opens on day 1 with 4000 shares at 3 15 per share Stock XYZ opens on day 1 with 5000 shares at 4 30 per share Stock QRS opens on day 1 with 6000 shares at 4 60 per share The price of stock ABC on day 8 begins at 3 50 The price of stock XYZ on day 8 begins at 3 90 Stock QRS opens on day 8 with a price of 4 50 per share Assume that each stock has the same number of shares that it opened with on day 1 What is the rate of change of this simple index over 1 week A 1 9 B 2 0 OC 2 0 D 1 9