A market in Boston orders oranges from Florida. The oranges are shipped to Boston from Florida by either railroad, truck, or airplane; an order can take 1,2,3, or 4 days to arrive in Boston once it is placed. The following probabilities have been assigned to the number of days it takes to receive order once it is placed (referred to as lead time):
Lead time

Probability

1

0.20

2

0.50

3

0.20

4

0.10

Total

1

Evaluate the expected number of days it takes to receive an order and the standard deviation.