A practitioner of family medicine begins her day with five patients needing urgent care. She does a very brief assessment of what each patient appears to need and estimates the time required of each

None of the cases is life-threatening, and so she determines to take the five in the order that they arrived at the clinic. The processing-time data for these patients, in the order they arrived, are: Patient A, 30 minutes; Patient B, 40 minutes; Patient C, 10 minutes; Patient D, 50 minutes; and Patient E, 15 minutes.
(a) If it is now 8:00 a.m., at what time will the doctor be finished with all five of these emergencies?
(b) How much time will the five patients have collectively spent waiting?
(c) How much less time would have been spent waiting if the doctor had taken the patients according to shortest processing time?

(a) Using first come, first served, all five patients will be finished in 145 minutes, or at 10:25 a.m.
(b) Total flow time is 455 minutes, of which 145 is for processing, and the remaining 310 is waiting time.
(c) If the doctor had used shortest processing time, the total flow time would have been 330 minutes, of which 185 is waiting time. In both cases, the doctor finished all patients at 10:25 a.m. A supporting table for each rule appears below.

Processing Time Due Date #Opns Order Flow time
A 30. 0. 0. first 30.
B 40. 0. 0. second 70.
C 10. 0. 0. third 80.
D 50. 0. 0. fourth 130.
E 15. 0. 0. fifth 145.
Total 455.
Average 91.
Average # jobs in the system 3.1379
Sequence: A, B, C, D, E

Processing Time Due Date #Opns Order Flow time
A 30. 0. 0. third 55.
B 40. 0. 0. fourth 95.
C 10. 0. 0. first 10.
D 50. 0. 0. fifth 145.
E 15. 0. 0. second 25.
Total 330.
Average 66.
Average # jobs in the system 2.2759
Sequence; C, E, A, B, D