A machine is used to fill plastic bottles with bleach. A sample of 18 bottles had a mean fill volume of 2.007 L and standard deviation of 0.010 L. The machine was then moved to another location. A sample of 10 bottles filled at the new location had a mean fill volume of 2.001 L and a standard deviation of 0.012 L. It is believed that moving the machine may have changed the mean fill volume, but is unlikely to have changed the standard deviations. Find a 99% confidence interval for the difference between the mean fill volumes at the two locations