A shipping firm suspects that the mean life of a certain brand of tire used by its trucks is more than 37,000 miles. To check the claim, the firm randomly selects and tests 18 of these tires and gets a mean lifetime of 37,700 miles with a standard deviation of 1200 miles. Assume the distribution is normal. At α = 0.05, test the shipping firm's claim. State the hypotheses:
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