Cost Management\perth

There was some question on exam according to cost estimate.

They give you optimistic, pessimistic and most likely values.

But, they don't mention anything about PERT.


So as I know there 2 methods estimate costs.


and Pert



There was 2 answers one of them the sum based on Pert, another - 3 point estimates.


I've chosen (O+M+P)/3 because they don't mention Pert technique needs to be used for estimates

PMBOK says that


Cost Estimates based on this equation (or even simple average of three points) may provide more accuracy and 3 points clarify the range of uncertainty of the cost estimates.

Please clarify answer