10 Question 4 (4 points) For their Christmas collection, a chocolate factory is going to use closed boxes in the form of decorated houses, with a content of 960 cm³. The dimensions of the house are given below, in terms of two variables x and y (in cm). 5x y 5x 6x 9x 6x 8x y y For the front and the back, a material will be used that costs 2 eurocent per cm², for all other sides the material costs 1 eurocent per cm². a) Show that the total cost C for the box (in eurocent) as a function of x is given by C = 240x² + 480 Χ You may use that the volume of the box is given by 60x2y (you do not have to show this). b) Find the values of x and y so that the cost for the box is minimal. What is the minimum cost?