The intensive care unit (ICU) at a certain hospital operates 24 hours a day. Polowin ate beow shows the minmum number of docrors that should be available during different periods. The hospital administration wants to determine how many doctors should report for work at the start of each time period in order to minimize the total staff required each day if: a) Doctors work a 12-hour shift. b) Doctors works either a 12-hour shift or a 24-hour shift