Now let's look at our forward pass using our critical path diagram. Which will give us our early start and early finishes in a projected project completion time. I'm using a slightly different model that makes it easier to understand and the calculations more clear. Before we begin, we need to define the node inputs. Please take a look at the key. We have ES representing early start. ACT as our activity or task, or work break down structure, or excuse me, work package. And EF as our early finish. The abbreviation DUR on the slides indicates the duration of the task. You'll also notice LS and LF. They are the late start and late finish, and we'll use those in the backward pass to calculate the critical path. But for this example, we're using our previous work breakdown structure and the task names, precedents and durations. So what do these things actually mean? Well, the early start is the earliest any activity task or work package can start if there are no changes to the schedule or there are no delays. The early finish is the earliest any activity, task or work package can finish considering your schedule, if there are no changes. The late start is the latest any activity, task, or work package can start without impacting the length of the entire project or project end date. And the late finish, or LF, is the latest any activity, task, or work package can end without impacting the project end date. So starting with activity A, all of our times are currently at 0. So now, what we're going to do is we're going to bring forward the early finish to both of the ES locations for activities B and C. Because they were both 0, now we need to move those forward. So we move those forward. So going across the top of the diagram, we take the 0 from A, and add the duration of task C which is 30. And that gives us our early finish for task C of 30. We then take that 30 and move it to the early start location to task E. We add the duration of 30 for task E, which gives us our early finish for E of 60. And now we take the 60 from the early finish of E and move it into the early start of F. We add 40, which brings the early finish to 100. Now we have to wait, because G is dependent upon both F and D. So we need to calculate the bottom in order to determine which value to place in the early start of G. Going back to the bottom row, we take the 0 from the start, and it moves to the early start of task B. To which we then add 5, for an early finish of 5. We take that 5 and move it to the early start of D, add the 15 from D which makes it our early finish 20. And now we have a dilemma, which branch do we use? Remember, this is the longest path to the completed project. And since G is dependent on both D and F, if D finishes in minute 20 and F during minute 100, we have to choose F. Because if we choose D, F isn't finish for another 80 minutes, it just doesn't work. So we move the 100 from task F into the early start of G. To which we add a duration of 10, for a total estimated early finished for G of 110 minutes. Now we can then transfer all those into our finished H, because there's no change. And since the duration is 0, the total early finish time is still 110 minutes, because there's no duration. That means that our planned time to finish is 110 minutes. If you remember back to the Gantt chart, total time we came up with is also 110 minutes. So as a recap, all right, we started at the beginning, took our early starts for each task. Added the durations for each task, which gave us our early finishes. We transferred those values into the early starts of the successor tasks all the way through the project. The only other thing that we needed to consider was which branch to use when both paths were required at that juncture. All right, but remember we use the higher value because it means that the task took longer in duration. And you can't move forward without it. And since we're looking for the critical path, we are looking for the longest path through the project. Also, this means that the earliest your project can be completed. So as you do this, this is the longest path. We now know that the critical path is A C E F G and H. And now we're going to confirm it. Now this actually goes back to our last diagram where we suspected that it was the case. But now we're going to confirm it using our backward pass. So this explains our forward pass. Now let's go and do our backward pass to confirm our critical path.