Question

A cell phone company’s profit is modeled by the function p(x) = 10x − x2 − 1, where p is expressed in thousands of dollars and x is the number of phones sold in hundreds. How many phones must the company sell to make a profit of more than $15,000?
between 200 and 400
between 200 and 800
between 600 and 1000
between 100 and 400
between 600 and 900