Two pain relief drugs are being considered. A random sample of 8 doses of the first drug showed that the average amount of time required before the drug was absorbed into the bloodstream was x1 = 24 minutes with population standard deviation = 4 minutes. For the second drug, a random sample of 10 doses showed the average time required for absorption was x2 = 29 minutes with population standard deviation = 3.9 minutes. Assume the absorption times follow a normal distribution. Should you use the critical value (zc) or (tc) in determining a confidence interval in this problem? Explain. Find a 90% confidence interval for the difference in average absorption time for the two drugs. Does it appear that one drug is absorbed faster than the other (at the 90% level)? Explain.