Customers arrive at a grocery store at an average of 2.1 per minute. Assume that the number of arrivals in a minute follows the Poisson distribution. Provide answers to the following to 3 decimal places.

What is the probability that exactly two customers arrive in a minute?

Find the probability that more than three customers arrive in a two-minute period.

What is the probability that at least seven customers arrive in three minutes, given that exactly two arrive in the first minute?