Given volume is 800 cm3.
Find the radius and height of the tank that requires the least amount of material.
I'm not quite sure how to do it.
Write the equation for total surface area of a cylinder,
including top and bottom discs if appropriate.
Use the volume value to write R in terms of h, or h in terms of R.
Write the surface area in terms of one variable.
Differentiate it with respect to that variable to find the minimum material.