We decompose the scope statement to create a WBS. We start with a high level and drill down to lower levels. Especially in this situation when its a new system, we do not know the details hence start with the top. [#2] Well, first of all, we know C & A are eliminated for use on a "new systems" project. However, there is a piece of information missing from the question which would make it difficult to choose between B & D. Generally, projects with less precedent (ie R&D or new products) are characterized by greater risk, particularly if they are also associated with high cost. A definitive (bottom-up) estimate could serve to mitigate the risk in that case because it is more accurate. However, it is also a more expensive and time-consuming type of estimate so what's missing from the question is whether or not you have the luxury of the time & money to invest in this approach. Remember that just because it is a "new systems" project doesn't mean a bottom-up estimate is precluded, because you could always approach it with the Moving Wave technique described in Kerzner, meaning that you take the first phase of the project down to WBS Level 4 and leave the second phase only roughly defined down to Level 2 until you've advanced far enough to be able to define it. However, since the magnitude of the project (in time & budget) is not given in this question, I would go with answer B. [#3] Top down approach is used only if you have enough historical information on the Project. in this case it is not true. Hence it would be appropriate to use Bottom up approach so, answer is B.