D. Answer the following problems.

1. Find the number in the interval [-5, 4] so that the difference of the number from its square is maximized,
2. An open-typed rectangular box is to be made from a piece of cardboard 30 cm long an 15 cm wide by cutting out identical squares from the four corners and turning up the sides. Find the volume of the largest rectangular box that be formed.
3. Determine the dimensions of the night circular cylinder of greatest volume that can be inscribed in a right circular cone of radius 10 cm and height 15 cm.​