There are painting jobs awaiting at a paint shop. Their processing times and due dates are shown in the table. The firm wants to determine the sequence of jobs according to shortest processing time (SPT). Jobs are assigned a letter in the order day arrived. What is the average number of jobs in the system? Today is day 1 and work begins today. Job Processing time (Days) Job Due Date (Days) A 6 10 B 4 9 C 5 7 D 3 9 E 19 22