Ten Different Families Are Tested for the Number of Litres $\overline { \mathrm { d } }$

Ten different families are tested for the number of litres of water they use per week before and after viewing a conservation video.Construct a 90% confidence interval for the mean of the difference of the "before" minus the "after" times if $\overline { \mathrm { d } }$ (before - after) = 4.8 and sd = 5.2451 $\begin{array} { l l l l l l l l l } \text { Before }&33 & 33 & 38 & 33 & 35 & 35 & 40 & 40 & 40&31\\\hline\end{array}$ After 34 28 25 28 35 33 31 28 35 33

A) (1.8,7.8)
B) (3.8,5.8)
C) (2.5,7.1)
D) (2.1,7.5)
E) (1.5,8.1)