An independent trucker has to choose one of the four possible combinations of inputs listed below. The two inputs are drivers and machinery. If he buys expensive machinery, then he can hire fewer drivers to deliver the same output. The input combinations are Method 1: 20 drivers, 10 machines; Method 2: 50 drivers, 2 machines; Method 3: 100 drivers, 0 machines; Method 4: 10 drivers, 12 machines. Hiring a driver costs $10. Each machine costs $100. Which method should he use?