Resistance Bands.... how many lbs of resistance?

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Is there a way I can figure out how many lbs of resistance my Sportline Pilates Resistance Tubing offers? I bought them at Zellers. There are three bands. The lightest resistance is a green band, then grey, then the highest is black. The resistance tubing I saw at Sportcheck was 2lbs, 5lbs and 10lbs rather then light, medium, heavy.... how can I figure out the resistance level in lbs of the tubing I bought at Zellers?