Two growth hormones are being considered. A random sample of 10 rats was given first hormone and their average weight gain was x(bar)1=2.3 pounds with the standard deviation s1=0.4. Fort second hormone, a random sample of 15 rates had an average weight gain of x(bar)2=1.9 pounds with standard deviation s2=0.2. Suppose the weight gains follow a normal distribution. Find a 90% confidence the interval for the difference in average weight gain for the two growth hormones.