Hey, could anyways help me with these two stat problems?

Urn 1 contains 5 green balls and 6 white balls. Urn 2 contains 3 green balls and 4 white balls. A ball is selected at random from Urn 1 and then transferred into Urn 2. A ball is then randomly selected from Urn 2. If the ball selected from Urn 2 was found to be green, what is the probability that the transferred ball was green?

A sales firm receives, on average, 5 calls per hour on its toll-free number. For any given hour, find the probability that it will receive between 4 and 6 (inclusive) calls. Use the Poisson approximation.

Thanks, totally clueless on how to do these!