In the production process shown below, the drilling operation occurs separately from, and simultaneously with, the cutting and polishing operations. A product needs to go through only one of the three assembly operations $($the operations are in parallel$).$ Cutting process: $15$ minutes$/$unit Polishing process: $10$ minutes$/$unit Drilling process: $25$ minutes$/$unit Pressing process: $40$ minutes$/$unit Assembly process: $60$ minutes$/$unit $($divided into $3$ assembly stations $-$ each station is $20$ minutes$/$unit$)$ Capacity and throughput If this company operates $8$ hours per day, $20$ days per month, the monthly capacity of the manufacturing process is: a$.960$ units$/$month b$.384$ units$/$month c$.160$ units$/$month d$.240$ units$/$month