Ten Different Families Are Tested for the Number of Litres

Multiple Choice

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)