Explain step by step please.

Assume that the population of paired differences is normally distributed. Answer only the following part and do not solve the entire confidence interval problem. 3) The table below shows the weights of 9 subjects before and after following a particular diet for two months. Subject A B C D E F G H I Before 168 180 157 132 202 124 190 210 171 After 162 178 145 125 171 126 180 195 163 Construct a 99% confidence interval for the mean difference of the "before" minus "after" weights. a) Identify the best point estimate for ud = ul-u2