19. The mean age (at inauguration) of all U. S. Presidents is approximately Normally distributed with a mean of 54.6. Barack Obama was 47 when he was
inaugurated, and his z-score was -1.21. What is the standard deviation of
presidents' ages?
(a) -9.20
(b) -6.28
(c) 6.28
(d) 7.60
(e) 9.20
What is the standard deviation of the presidents age?

Exclude leap years from the following calculations. (a) compute the probability that a randomly selected person does not have a birthday on october 4. (type an integer or a decimal rounded to three decimal places as needed.) (b) compute the probability that a randomly selected person does not have a birthday on the 1st day of a month. (type an integer or a decimal rounded to three decimal places as needed.) (c) compute the probability that a randomly selected person does not have a birthday on the 30th day of a month. (type an integer or a decimal rounded to three decimal places as needed.) (d) compute the probability that a randomly selected person was not born in january. (type an integer or a decimal rounded to three decimal places as needed.)