Question: At Bank A, a random sample of 16 customers spent a mean time of 89 seconds at a money machine with a standard deviation of 14 seconds. At Bank B, a random sample of 20 customers spent a mean time of 85 seconds at a money machine with a standard deviation of 15 seconds. Assume that the populations are normally distributed with unequal variances. Construct a 99% confidence interval for the difference between population means, \({{\mu }_{A}}-{{\mu }_{B}}\)