Leslie, a park manager, wants to determine if there are enough swings to go around in one of the local parks. She goes to the park and develops
the following probability model for the usage level of the swings. How many swings are in use, on average?
Number of swings in use 0 1 2 3 4 5 6 7
Probability
0.14 0.21 0.28 0.21 0.10 0.02 0.04