A revenue function is an equation that shows how much revenue a factory will generate at a given price. Suppose a manufacturer of calculators has determined that, for a particular model of calculator, the revenue function is R = -150p2 +21000p where p is the retail price (in dollars) of the calculator and R = f(p) is the revenue generated from the calculator sales (in dollars). Please graph this equation and tell what is the lowest price at which $600,000 could be earned?