a) A rectangular advertisement board will be set up beside the main road of a crowded traffic junction. The printed material on the advertisement board will occupy 50 m of the area. In order to allow sufficient support to erect the advertisement board, it is suggested to have the margins of 0.5 m at the top and bottom and 1 m at each side. Please estimate the most economical overall area of the advertisement board which meets the specifications. [Differentiation quotient rule:(3)' = sqrtie'] (15 marks) g2