8. (10%) A rectangular solid is measured to have length x, width y} and height z, but each measurement may be in error by 1%. The estimated percentage error in calculating the volume is____

9. (10%) A closed rectangular box whose volume is 128 cubic inches is to be made with a square base. If the material for the top and bottom costs twice as much per square inch as the material for the sides, use Lagrange Multipliers to find the dimensions of the box that minimize the cost of material.