Suppose f(x, y) = xy + 5. Determine each of the following: f(4,-5)= f(-5,4)= f(0,0)= f(-1,-5)= f(t, 6t)= f(uv, u - v)= A car rental company charges 40 dollars per day, 12 cents per kilometre driven, and a 20 dollar one-time processing fee for a car rental. (a) Write a formula for the cost C (in dollars) of renting a car as a function of the number of days d and the number of kilometres driven k. C = (b) If C = f(d, k), then f(3,800) = dollars. Find the indicated partial derivatives of: fx(x, y) = fy(x, y) = f(x, y) = -8x+4y 4x 6y Find the indicated partial derivatives of: e4y f(x, y) = xye of = of = 5555 Find the indicated partial derivatives of: at the point (x, y) = (4,1). of (4, 1) = off (4,1) = f(x, y) 3x-2y = 3x + 2y