Gloria would like to construct a box with volume of exactly 40ft3 using only metal and wood. The metal costs $12/ft2 and the wood costs $6/ft2. If the wood is to go on the sides, the metal is to go on the top and bottom, and if the length of the base is to be 3 times the width of the base, find the dimensions of the box that will minimize the cost of construction. Round your answer to the nearest two decimal places.