Over 500 million tweets are sent per day.Assume that the number of tweets per hour follows a Poisson distribution and that Bob receives on average7tweetsduring his lunch hour. (Round your answers to four decimal places.)

(a)

What is the probability that Bob receives no tweets during his lunch hour?

(b)

What is the probability that Bob receives at least 4 tweets during his lunch hour?

(c)

What is the expected number of tweets Bob receives during the first 30 minutes of his lunch hour?

(d)

What is the probability that Bob receives no tweets during the first 30 minutes of his lunch hour?