An investor creates his own stock market index that she uses to measure the value of a company. The Nonstandard and Poorly Index he proposes is NPI = f(p, s) = 0.60 . p . s index units, for a company with a stock price of p (dollars per share) and a number of issued shares s (in thousands). (a) Compute fp(25, 30). (b) Write a complete sentence interpreting what your computation from part a means in the applied context, including units. Demand for Orange mattresses is given by D(x, y) = (20 + 2y)e-0.1 daily mattresses sold when Orange mattresses are sold for a hundred dollars each and competitor Ghost mattresses are sold for y hundred dollars each. (a) Compute Dry. (b) Suppose that demand for Ghost mattresses is given by G(x, y) = 30 + 0.02x -0.ly. Compute partial derivatives to show that Orange and Ghost mattresses are substitute goods