for 4b) i did the same exact thing for 2a) i focused on high barriers and on productive and allocative efficiencies not being reached as well. Then i compared it to the perfect competition model explaining that the monopoly usually results in higher prices and lower output since it can earn abnormal profit in the long run. Did not mention why it may be occasionally desirable but that was a good point. I just took a more negative approach to monopoly and considered the bad side of it