. A square piece of cardboard with side length 40 cm is used to create an open-topped box by cutting out squares with side length x from each corner.
a) Determine a simplified expression for the surface area of the box.
b)Determine any restrictions on the value of x.
2. For the open-topped box in question 1, determine a simplified expression for the ratio of the volume to the surface area. What are the restrictions on x?