Well, we know the length, 0.36, and when we take the case where we sort of reach the end of the Hooke's Law parameter space, we have a delta I which is 425 times lower than this, so we have 20 divided by 425, and that is, um... four point seven times ten to the minus two, but that is in terms of centimeters and we want it in terms of meters, so we have to multiply by another factor ten to the minus two. 