During the evening hours of 7 PM. until 9 P.M., the number of calls received at a Macy's customer service line can be modeled as a Poisson distribution with a mean of 7 calls per 30 minutes The probability of zero calls in a 30-minute period $ 0,0604 al The mean number of calls received at the hotline between 7 P.M. and 9 P.M. on a given night ist b) The standard deviation is: The probability of getting zero calls between 7:30 P.M. and 8:00 P.M. is: (Hint: there are two ways to solve this problem.) Edit Format Table 12pt Paragraph