Ten Different Families Are Tested for the Number of Litres

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
(before-after) = 4.8 and
=5.2451

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)