The difference between the number of customers in line at the express checkout and the number in line at the superexpress checkout is x1 - x2. calculate the expected difference.

The table is:0 1 2 3

x1 0 0.08 0.06 0.04 0.00

1 0.05 0.18 0.05 0.03

2 0.05 0.04 0.10 0.06

3 0.00 0.03 0.04 0.07

4 0.00 0.01 0.05 0.06

Expected difference =

+ (0.08 * (0-0)) + (0.06 * (0-1)) + (0.04 * (0-2)) + (0.00 * (0-3)) + (0.05 * (1-0)) + (0.18 * (1-1)) + (0.05 * (1-2)) + (0.03 * (1-3)) + (0.05 * (2-0)) + (0.04 * (2-1)) + (0.10 * (2-2)) + (0.06 * (2-3)) + (0.00 * (3-0)) + (0.03 * (3-1)) + (0.04 * (3-2)) + (0.07 * (3-3)) + (0.00 * (4-0)) + (0.01 * (4-1)) + (0.05 * (4-2)) + (0.06 * (4-3))

= 0.17