3. (a) Explain the purpose of activity network diagrams in project planning. (6) A certain project consists of activities labeled as A through L. The following table gives the estimated time duration for each activity with proceeding activities needed to be completed before the commencement of it. Proceeding activities Activity A B Time (days) 6 11 10 + + + 4 D E F G H 3 12 6 9 3 7 5 B B C.F B , , DJ G, I K 1) Construct the network diagram for the above project and find the project duration and mark the critical activities. (11) Find the total float for all the activities and the activities that can be delayed without affecting the project completion time. (111) If the activity D takes 6 extra days to complete, what would be the project duration? (iv) If the activity A is delayed by 4 weeks, will the project completion time change? Explain your