Steel produced by company A has an average tensile strength of 4500 lbs and a variance of 40000 lbs, while those produced by company B have an average tensile strength of 4000 lbs and a variance of 90000 lbs. Suppose 50 random samples are taken from company A and 100 random samples are taken from company B, what is the probability that the average difference in tensile strength of the two samples is greater than 600 lbs?

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