Implement the additional statistic$-$collection function described in Exercise $2-1,$ and add a plot that tracks the total number of parts in the system $($also called work in process, abbreviated as WIP$)$ over time. Note that, at any given point in simulated time, WIP is the number in queue plus the number in service; you can use the WIP module from the Input Output panel to define a point at which you wish to begin tracking WIP by incrementing a variable you have defined and use the same module to decrement from that same variable when it has left the area for which you are tracking WIP.