How would these problems concerning probability and t values be approached?

\f\f\f\fThe amount of time that a drive-through bank teller spends on a customer is a random variable with a mean pi = 5.5 minutes and a standard deviation 0 = 2.4 minutes. If a random sample of 36 customers is observed, nd the probability that their mean time at the teller's window is (a) at most 4.5 minutes; (b) more than 6.3 minutes; (0) at least 5.5 minutes but less than 6.1 minutes. A random sample of size 36 is taken from a normal population having a mean of 70 and a standard deviation of 2. A second random sample of size 64 is taken from a different normal population having a mean of 65 and a standard deviation of 5. Find the probability that the sample mean computed from the 36 measurements will exceed the sample mean computed from the 64 measurements by at least 3.7 but less than 5.4. Assume the difference of the means to be measured to the nearest tenth. \f\f\f\f\f