The number of online customer service chats of a small company is believed to follow a Poison distribution. Currently, these chats are handled by a single agent. The manager of the company knows from past experience that an additional agent will be needed if the rate of incoming online chats exceeds 10 per hour. During a randomly selected half-hour period, there were 7 chats observed. a) If the rate of online chats is actually 10 per hour, find the probability that 7 or more chats will come in during a given half-hour period.