The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x, be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9200 observations, the sample mean interval was x, = 61.6 minutes. Let x, be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 25,457 observations, the sample mean time interval was x, = 69.4 minutes. Historical data suggest that of = 8.07 minutes and o, = 12.06 minutes. Let #, be the population mean of x, and let u, be the population mean of x,. (a) Compute a 90% confidence interval for 1 - #2. (Use 2 decimal places.) lower limit upper limit