Answer:
(a) 
(b) 0.7910
(c) 0.0401
(d) 0.6464
Step-by-step explanation:
Let <em>X</em> = amount of time that people spend at Grover Hot Springs.
The random variable <em>X</em> is normally distributed with a mean of 73 minutes and a standard deviation of 16 minutes.
(a)
The distribution of the random variable <em>X</em> is:

(b)
Compute the probability that a randomly selected person at the hot springs stays longer than 60 minutes as follows:

*Use a <em>z</em>-table for the probability.
Thus, the probability that a randomly selected person at the hot springs stays longer than an hour is 0.7910.
(c)
Compute the probability that a randomly selected person at the hot springs stays less than 45 minutes as follows:

*Use a <em>z</em>-table for the probability.
Thus, the probability that a randomly selected person at the hot springs stays less than 45 minutes is 0.0401.
(d)
Compute the probability that a randomly person spends between 60 and 90 minutes at the hot springs as follows:

*Use a <em>z</em>-table for the probability.
Thus, the probability that a randomly person spends between 60 and 90 minutes at the hot springs is 0.6464