You are to make a rectangular tray measuring 45x30 cm, with a depth of 12 cm in ABS. An acceptable tray can be produced by thermoforming 3 mm thick extruded sheet, which is available as 200x120 cm sheets at $2300 per metric ton. It would be necessary to use blanks measuring 55x40 cm, which would be trimmed to 47x32 cm after forming. For thermoforming, the mold would cost $4000, cycle time would be 90 seconds and total factory costs would be $12 per hour. A somewhat better tray, weighing 495 grams, could be made by injection molding. The mold cost is $16,000, cycle time is 30 seconds and factory costs are $25 per hour. A scrap rate of 5% can be assumed. Molding granules cost $1600 per metric ton. Scrap from either process can be sold at $500 per metric ton. Calculate the minimum number of trays you would have to make to justify injection molding. I have seen some solution for this question,where its mentioned that 4 trays can manufactured from one sheet, then they did the calculations. My question is how do we figure out that we can make 4 trays from one sheet?