Let X denote the outstanding balances of customers of a firm. From past experiences X is well aproximated by a normal distribution with mean 45 and...

Let X denote the outstanding balances of customers of a firm. From past experiences X is well aproximated by a normal distribution with mean 45 and variance 100. If an auditor takes a random sample of 36 accounts what is the probability that the mean balance will be less than 45? (Your answer should be correct to one decimal place.)