When some software companies develop software, they do it with "planned obsolescence"
in mind. This means that they plan on the sale of the software to rise, hit a point of
maximum sales, then drop and eventually stop when they release a newer version of the
software. Suppose a graph of the curve showing the number of sales over time can be
modeled with a parabola and that the company plans on the "life span" of its product to be
6 months, with maximum sales reaching 1.5 million units. Write an equation that models
this situation.