3. (a) Find dxdy,dx2d2y and dx3d3y of y=x2+x360 (3 marks) (b) A company designed a new product with the shape of an equilateral triangular prism which is shown in Figure B3. The costs of package are 3 cents /cm2 for the surface of triangle side and 2cents/cm2 for the surface of rectangle side. The volume of the product is 34.64 cm3. Figure B3 (i) Express the volume of the product in terms of x and l. (Hint: Area of triangle =21absin ) (1 marks) (ii) Express l in terms of x. (2 marks) (iii) Let C be the Costs of package for the surface of a product and (4 marks) in terms of x only, show that C=23x2+x480 cents /cm2. (iv) Find dxdC and dx2d2C. (4 marks) (v) Determine the value of x and state it is maximum or minimum ( 6 marks)