How would be the proper way to solve this problem

An open-topped water tank is to be made of sheet metal so that it has a volume of 201 m3. It is to have a circular base of diameter x metres and vertical sides of height h metres. (a) Using the Lagrange multiplier method, find values of diameter and height such that the amount of sheet metal used is minimised.(Round your answers to the nearest centimetre.) (10 marks) (b) Show that the solution in part (a) satisfies the second order conditions for a local minimum. (5 marks) (c) Interpret lambda (M from part (a)