First find the screen area of Bill's TV: 48 inches * 100 inches = <<48*100=4800>>4800 square inches
Then find the screen area of Bob's TV: 70 inches * 60 inches = <<70*60=4200>>4200 square inches
Then subtract the size of the smaller TV from the size of the bigger TV to find the size difference: 4800 square inches - 4200 square inches = <<4800-4200=600>>600 square inches
Then multiply the size difference by the weight per square inch to find the weight difference: 600 square inches * 4 oz/square inch = <<600*4=2400>>2400 oz
Then divide the weight difference in ounces by the number of ounces per pound to find the weight difference in pounds: 2400 oz / 16 oz/pound = <<2400/16=150>>150 pounds
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