Commuting to work. A commuter must pass through five traffic lights on her way to work and will have to stop at each one that is red. After keeping a record for several months, she developed the following probability model for the number of red lights she hits:

X  # of Red 0 1 2 3 4 5 p1X  x2 0.05 0.25 0.35 0.15 0.15 0.05

a) How many red lights should she expect to hit each day?

b) What’s the standard deviation?