21) A father notes that when his teenage daughter uses the telephone, she takes not less than 6 minutes for a call and sometimes as much as an hour. Fifteen minutes call are more frequent than calls of any other duration. If these phone calls were an activity in PERT project, then phone calls expected duration will be

22) What estimate would you give for the variance in above problem

23) The time by which a particular activity can be delayed without affecting the preceding and succeeding activities is known as

24) The time with which direct cost does not reduce with the increase in time is known as

25) The time corresponding to minimum total project cost is