Well, it can be easily done by differentiating function of area with respect to one of either height or radii/diameter (if calculus is enabled).say:A=pir^2 + 2pirhV=pir^2h or h=V/(pir^2)thenA=pir^2 + 2pirV/(pir^2)to minimize surface area, we make dA/dr = 0try to do the rest, you'll find 2r = h