"For a showing of a specific movie, an AMC theater estimates that 120 people will attend if it is not raining. If it is raining, the theater estimates that 200 people will attend. The meteorologist predicts a 70% chance of rain tomorrow. Determine the expected number of people who will attend the movie."

I did E(X) = (200*7/10) + (120*3/10) to get 176 people, but I have no idea if I did this correctly.