Problem from the book Scheduling: Theory, Algorithms and Systems, Fifth Ed by Michael L Pinedo Chapter 2, problem 2.1. I posted this solution before but I could not get the explanation of the process, can you please explain me step by step...

2.1. Consider the instance of 1 11 wjCj with the following processing times and weights. jobs 1 2 3 4 w 6 11 9 5 Pi 3 5 7 4 (a) Find the optimal sequence and compute the value of the objective. (b) Give an argument for positioning jobs with larger weight more towards the beginning of the sequence and jobs with smaller weight more towards the end of the sequence. Exercises 29 (c) Give an argument for positioning jobs with smaller processing time more towards the beginning of the sequence and jobs with larger processing time more towards the end of the sequence. (d) Determine which one of the following two generic rules is the most suitable for the problem: (i) sequence the jobs in decreasing order of wj -pj; (ii) sequence the jobs in decreasing order of wj/pj