The manager of a local gym has determined that the length of time patrons spend at the gym is a normally distributed variable with a mean of 80 minutes and a standard deviation of 20 minutes. (a) What...

The manager of a local gym has determined that the length of time patrons spend at
the gym is a normally distributed variable with a mean of 80 minutes and a standard
deviation of 20 minutes.

(a) What is the least amount of time spent by 60% of patrons at the gym?
(b) What proportion of patrons spend more than two hours at the gym?
(c) What proportion of patrons spend less than one hour at the gym?