A project manager is negitoating with a contractor. Neither has a good idea of how long the project will take, or how much the materials will cost. Which contract type is MOST appropriate for this project?

A. CPFF

B. T&M

C. CPAF

D. FFP

According to Headfirst the right answer is B) T&M

While I reread the question, what impresses me is the PM doesnt know how long project will take. So it might be for a long period and T&M is not appropriate. Also it doesnt mention anything about incomplete scope. So why not to chose FFP?