(Hint: to find the maximum, you will have to derive the function partially with respect to x and with respect to y, and in both cases set zero and solve for each variable.)

5) The profit function defined by f(x, y) = -2x2 - 2xy - 2y2 + 36x + 42y - 158 for all (x, y) it has a maximum. Find them. (Hint: to find the maximum, you will have to derive the function partially with respect to x and with respect to y, and in both cases set zero and solve for each variable.)