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17. An oil tank is cylindrical in shape and is closed at both ends. If the radius and volume are / and V, show that the total surface area A is given by 4 = 2² +2 If Vis

m², find the value of which makes A a minimum.

18. A solid consists of a cylinder, of radius r and height h, and a cone, of radius r and height 12, attached as shown. If the volume of the cylinder is 24x cm³, find the value of r for which the total surface area of the solid, including the base of the cylinder, is minimum (The curved surface area of a cone of radius rand slant height / is rl)

here​