please help with Q4. will upvote if helpful. thanks.

Question 4 A contract for the erection of prefabricated classrooms has been awarded to Vinnigrig CC. You are the cost accountant of the firm and have identified the activities involved, and the sequence thereof, as follows: The duration of the various activities in normal and accelerated circumstances, and the relevant slopes are as follows: Activity Duration in days Normal Accelerated Cost Slope (R) 10 1800 A B A AD 10 6 2800 1200 4700 4000 800 BG CE DF E-G F G I 5 8 1500 1200 1700 6 The fixed costs amount to R4500 per day. They are not regarded as committed fixed costs. Determine the critical path and determine the programme to be followed in order to complete the project at the minimum cost and indicate the saving in normal costs