6. A Norman window is in the shape or rectangle surmounted by a semi circle. What is the ratio of the. Width of the rectangle to the total height so that it willyield a window admitting the most light for a given perimeter?

7. The volume or the closed cylinder tank is 11.3 cubic meter. If the total surface area is a minimum, what 1s its base radius, in m?

8. The distance of the body travel is a function of the time and is given byx(t) =16t+8t^ { 2}. Find its velocity at t=3