Suppose that 100 units of a product are demanded when the price is $ 10 per unit and 120 when the price is $ 8 per unit. If the demand function behaves linearly, set up the equation for the quantity demanded as a function of the price and use it to obtain the price of the product if the quantity demanded was 90 units. Select the correct option.

$12

$9

$7

$11

$13