The marginal cost function of a product is given by 20x + 25 and when 20 units are produced, the total cost is $25000.00. Determine the total cost when the number of units is 40. Determine the area under the curve f(x) =12x3 + 3x2 + 2x -5 on the interval [1, 21 Given the following function: f (x, y) = 3x2 + 4x2 y+ xy+5y? Determine, 1. f(2,-1) iii. Jy iv. Ja v. Joy vi. Jo D. Determine the critical point(s) of f (x, y) = x2- y2. E. Classify the critical point(s)