David bought a cell-phone for R2500. He sold it to his friend for 25% more. How much did he sell it for?

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?

Plzzz answer both questions and i will give you 100 points

Will give brainliest b. describe the function over each part of its domain. state whether it is constant, increasing, or decreasing, and state the slope over each part.