The function S=5000 +200x and D=9500-100x express the supply S and the demand D, respectively, for a popular compact disc brand as a function of its price x (in dollars).
a) Graph the functions on the same coordinate system.
b) What happens to the supply as the price increase?
c) What happens to the demand as the price increases?
d) The price at which supply and demand are equal is called the equilibrium price. What is the equilibrium price?