Lead Time Is Exactly 20 Days Long

Multiple Choice

Lead time is exactly 20 days long.Daily demand is normally distributed with a mean of 10 gallons per day and a standard deviation of 2 gallons.What is the standard deviation of demand during lead time?

A) 20 x 2
B) 20 x 10
C) 2 times the square root of 20
D) 2 times the square root of 10
E) none of the above