A furnace wall is to be designed to transmit a maximum heat flux of 200 Btu/h ft² of wall area. The inside and outside wall temperatures are to be 2000°F and 300°F, respectively. Determine the most economical arrangement of bricks measuring 9 by 4 ½ by 3 in. if they are made from two materials, one with a k of 0.44 Btu/h ft °F and a maximum usable temperature of 1500°F and other with a k of 0.94 Btu/h ft °F and a maximum usable temperature of 2200°F. Bricks made of each material cost the same amount and may be laid in any manner.