10.46 Part of a testing program on a family of dual bell rockets designed to compensate for low-altitude performance led to two slightly different new designs. The two sets of test flow rates, measured in pounds per second, resulted from testing these two new designs.

n  x  x 2 Design 1 36 278.4 2163.76 Design 2 42 310.8 2332.26 Determine the 99% confidence interval for the difference between the two mean test flow rates. Assume normality.