12 days
     ------>A=5days----->B=7days---
     |                            |
START|                            |----->E=17days-->FINISH
     |                            |
     ------>C=3days----->D=11days--
                  14 days

Time To Finish = 31 days
Human Days = 43 days
Human Hours = 43x8 = 344 hours
Cost = 344hours x $50/hour = $17,200 
Critical Path: C-D-E
Put the Senior Engineer on the critical path (C-D-E)
Put the Junior Engineer on the other path (A-B-E)







Let us say task B is a very specialized task, and due to layoffs, there is only one person who can do it - Wendy. Wendy is not available until after two weeks (10 working days, or 5 days after A is complete).

                  17 days
     ------>A=5days-->DELAY=5days-->B=7days---
     |                                       |
START|                                       |----->E=17days-->FINISH
     |                                       |
     ------>C=3days----->D=11days-------------
                  14 days

Time To Finish = 34 days
Human Days = 43 days
Human Hours = 43x8 = 344 hours
Cost = 344hours x $50/hour = $17,200 
Critical Path: A-B-E
Put the Senior Engineer on the critical path (C-D-E)
Put the Junior Engineer on the other path (A-B-E)