19 hours
5
9am, 10am, 11am, 12pm, 1pm, 2pm, 3pm, 4pm, 5pm. 8 hours.
12am to 4pm is 16 hours.
6 hours from 4pm to 10pm
22
7am to 4pm is 9 hours.
4pm to midnight is 8 hours.
72
10am to 4pm is a period of six hours.
On the same morning there are 3 hours from 8am to 11am
11am to 12 is 1 hour 12 to 5pm is 5 hours → 11am to 5pm is 1 + 5 = 6 hours