A solid rectangular block has a square base of side x cm. The height of the block is h cm and the total surface area of the block is 96 cm. (1) Express h in terms of x and show that the volume, Vcm', of the block is given by V = 24x-x. Given that x can vary. (ii) find the stationary value of V. (iii) determine whether this stationary value is a maximum or a minimum. [3] [3] [2]