The monthly profit (in dollars) of Bond and Barker Department Store depends on the level of inventory x (in thousands of dollars) and the floor space y (in thousands of square feet) available for display of the merchandise, as given by the equation below.
P(x, y) = -0.016x^2 - 17y^2 + xy + 28x + 22y - 20000
(a) Compute Px and Py when x = 4000 and y = 150.
Px = ?
Py = ?
(b) Repeat with x = 5000 and y = 150.
Px = ?
Py = ?