Suppose that a when a cell phone store charges $20 it sells 27 units. When it drops the price to $19 it sells 28 units. Assume that demand is a linear function of price. If each phone charger costs $1 to make, what price should the store charge to maximize its profit?
If x is the number of times the price is reduced by one dollar. Find a function for total profit with respect to x. A negative value for x will mean the price is increased.
f(x)=?