Consider a rectangle whose base x and height y change with respect to time. At this moment, the base is 30 m and is increasing at a rate of 10 m{s, and the height is 40 m and is decreasing at a rate of 5 m{s. (a) (i) Express the area A of the rectangle in terms of x and y. (ii) Find the rate of change of A changing at this moment. (b) (i) Express the diagonal D of the rectangle in terms of x and y. (ii) Find the rate of change of D changing at this moment.