Please help with steps and explanations I am very confused how to do these calc problems

1. A box with a square base and open top must have a volume of 32,000 cm'. Find the dimensions of the box that minimize the amount of material used. 2. The velocity graph of a braking car is shown. Use it to estimate the distance traveled by the car while the brakes are applied. (fu/s) 60 (seconds) 3. A spotlight on the ground shines on a wall 12 m away. If a man 2 m tall walks from the spotlight toward the building at a speed of 1.6 m/s. how fast is the length of his shadow on the building decreasing when he is 4 m from the building