Bob runs a large animal shelter. At Bob's shelter, the length of
stay for puppies has a mean of 78 days and a standard
deviation of 12 days. The Smith family adopted a puppy
named Birdie from the shelter. When Birdie was adopted, she had
been at the shelter for 91 days.
Find the z-score of Birdie's length of stay at the shelter
relative to the lengths of stay for all the puppies at the shelter.
Round your answer to two decimal places.