Consider a project with six activities. The CPM method has already been implemented, with the results shown in the file P15_38.xlsx. (All times are in months.) This file also shows the number of workers of type A, the number of workers of type B, and the material costs per month for each of the activities.

Workers of type A receive $1600 per month, and workers of type B receive $2400 per month.

a. Create a table and then an associated line chart that shows the monthly cash flows through the end of the project when each activity is started at its earliest start time and when it is started at its latest start time.

That is, two series should be plotted on the chart.

b. Suppose the company in charge of this project wants to find the start times for the activities so that the NPV of the cash flows is minimized, using an annual discount rate of 10%. Create a Solver model to do this. The only constraints are that the start times must be within their earliest and latest start time ranges.