Suppose you currently own a sugar shack and the only good you sell is maple syrup. From experience, you observe that when you set the price of a one-liter bottle of maple syrup at P = $10, you can sell 40 bottles everyday. If you raise the price to P = $12, you can sell 30 bottles only. Suppose you use this information to estimate the linear, "point-slope" demand equation for your maple syrup. Which of the prices below will maximize your total revenue?

a.

$8

b.

$9

c.

$11

d.

$13