4. [30 points) Five workers are available to perform four jobs. The time it takes each worker to perform each job is given in the following table. The goal is to assign workers to jobs so as to minimize the total time required to perform the five jobs: Job 2 Worker 1 Time Job 3 10 20 Job 4 15 16 Job 5 16 15 8 2 3 4 5 Job 1 10 12 12 6 16 9 12 12 12 15 18 18 14 22 8 8 12 8 a. Which worker should be assigned to which job? What is the total time required? (Hint: Use the Assignment model). b. If there are only 4 jobs (assume that job 5 is not required), how would the workers be assigned to jobs? (Hint: Change the constraints in the Assignment model)