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?