The heights of pecan trees are normally distributed with a mean of 10 feet and a standard deviation of 2 feet.

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(a) For a sample of 64 pecan trees, state the standard deviation of the sample mean (the "standard error of the mean"). (Round your answer to three decimal places)

(b) Suppose a sample of 64 pecan trees is taken. Find the probability that the sample mean heights is between 9.5 and 10 feet. (Round your answer to four decimal places)