a wooden bookshelf has external dimensions as follows: height=110 cm depth=25 cm breadth=85 cm the thickness of the plank is 5 cm everywhere. the external faces are to be polished and the internal faces of the shelf are to be painted. if the rate of polishing is 20p. per cm^2 and the rate of painting is 10p. per cm^2 , find the total expenses of polishing and painting the surface of the bookshelf