Solve the problem.
From a thin piece of cardboard 30 cm × 30 cm, square corners are cut out so that the sides can be folded up to make a box. What dimensions will yield a box of maximum volume? What is the maximum volume?
◦ 10 cm × 10 cm × 10 cm; 1000 cm3
◦ 20 cm × 20 cm × 5 cm; 2000 cm3
◦ 24 cm × 24 cm × 3 cm; 1728 cm3
◦ 22 cm × 22 cm × 4 cm; 1936 cm3