You are the scheduler in a machining shop for heavy parts. Four jobs will arrive at your workshop today. All of them need five operations in the same sequence: turning, milling, boring, grinding and polishing. The operation times (working days) are listed in the following table: Operations Turning Milling Boring Grinding Polishing Jobs A 15 5 6 10 10 5 B 6 13 15 7 5 C 11 7 8 5 7 D _ 12 18 _ 15 20 20 Please arrange the production schedule for these jobs, using Palmer's Algorithm. Please also draw a Gantt chart and calculate the makespan.