Hi,
 Im preparing for PMP and have a question on Estimate Activity Duration process. Why does PMBOK has a process called "Estimate Activity Duration" and does not have a process called "Estimate Activity Effort"? PMBOK suggest to use Activity Duration Estimate to calculate cost.  

  As an example if we consider an activity, painting a room, is going to take 8 hours of effort and if the resource is allocated 50% per day, the duration goes to two days. Where as we should pay for 8 hours of
work. If we consider the duration to estimate the cost, it is misleading since we would end up paying for two days(since the duration is two days). Could someone please clarify my doubt.

Regards,
Sundar.