A compressor manufacturer is testing two different designs for an air tank. Testing involves pumping air into a tank until it bursts, then noting the air pressure just prior to tank failure. Four tanks of design A are found to fail at an average of 1400 pounds per square inch (psi), with a standard deviation of 250 psi. Six tanks of design B fail at an average of 1620 psi, with a standard deviation of 230 psi. Assuming normal populations with equal standard deviations, use the 0.10 level of significance in comparing the two designs. Construct and interpret the 90% confidence interval for the difference between the population means.