16. A cover page of a textbook is to have an area of 90 in², with one inch margins at the bottom and sides and a ½ inch margin at the top. Find the dimensions of the cover page that will allow largest printed area. 17. Open Air Waste Management is designing a rectangular construction dumpster with open top that will be twice as long as it is wide and must hold 12 m³ of debris. Find the dimensions of the dumpster that will minimize its surface area. 18. Amira wants to construct a box whose base length is 3 times the base width. The material used to build the top and bottom cost RM 10 /cm² and the material used to build the sides cost RM 6/cm². If the box must have a volume of 50 cm³, determine the minimum cost to build the box.