You are constructing a closed box whose length, /, is three times its width, w, as indicated in the labels on the figure below The material costs $5 per square inch for the top and bottom and $3 per square inch for the sides. The box must hold 60 cubic inc 31 (a) Write an equation for the cost of the box in terms of w and h O C . 12wh + 10w OC = 36wh + 30w2 O C = 12wh + 30w2 O C = 4wh + 2w2 O C = 8 wh + 6w2 O C = 24wh + 30w2 (b) Write an equation for the cost in terms of w only. Use lower case w. C(W) = (c) Find C'(w) = (d) Find the exact width that minimizes the cost of the box. W= inches