quadratic function

Question

A local conservation groups makes and sells shirts to raise money for its projects. The materials for each shirt is set to $6, and the group sells an average of 20 shirts per week at a price of $10 each. The group has been considering raising the price, so it conducted a survey and finds that for every dollar increase, it will lose 2 sales per week.
• Find a quadratic function that models weekly profit in terms of price per shirt.
• Graph the function.
• What price should the group charge for each shirt to
maximize profits?

 

Answer 1

I can at least solve the first part:

earnings = sales * (price - 6)

sales = 20 - 2(price - 10)

earnings = (20 - 2(price - 10))(price - 6)