I want to write 3 paragraphs about the statistics ?

1- I want to write 3 paragraphs about the statistics when you did not use optimistic and pessimistic on the budget?

2-I will attached file that includes the specific informations about the question , but I do not want to do all the question just do the part two ..

3- This is the part two>>>>>

Part II

Many (if not most) project managers will formulate the budget with single forecasts for each line item, perhaps as below.

Write 3 paragraphs (one single spaced page or less) describing the disadvantages of this approach and the problems it might cause in practice.