Construct a Confidence Interval for µD, the Mean of the Differences

Multiple Choice

Construct a confidence interval for µd, the mean of the differences d for the population of paired data. Assume that the population of paired differences is normally distributed.
-The table below shows the weights of 9 subjects before and after following a particular diet for two months. $\begin{array}{ c | r r r r r r r } \text { Subject } & A & B & C & D & E & F & G&H&I \\\hline \text { Before } & 168&180&157&132&202&124&190&210&171 \\\hline \text { After } &162&178&145&125&171&126&180&195&163\end{array}$
Construct a $99 \%$ confidence interval for the mean difference of the "before" minus "after" weights.

A) $- 0.6 < \mu _ { \mathrm { d } } < 20.4$
B) $4.51 < \mu _ { \mathrm { d } } < 15.7$
C) $2.4 < \mu _ { \mathrm { d } } < 17.4$
D) $2.8 < \mu _ { \mathrm { d } } < 17.0$