Please help me to find the correct solution to the red part. -0.63 is not the correct answer:

The concentration of active ingredient in a liquid laundry detergent is thought to be affected by the type of catalyst used in the process. The standard deviation of active concentration is known to be 3 grams per liter, regardless of the catalyst type. Ten observations on concentration are taken with each catalyst, and the data follow: Catalyst 1: 57.8, 66.6, 65.4, 65.4, 65.2, 62.6, 67.6, 63.7, 67.2, 71.0 Catalyst 2: 68.0, 71.9, 70.3, 69.3, 64.8, 69.6, 68.6, 69.4, 65.3, 68.8 (a) Find a 95% two-sided confidence interval on the difference in mean active concentrations for the two catalysts. X -6.07 SH1 - H2 5 -0.63 Round your answer to two decimal places (e.g. 98.76)