Help with Scheduling Practice Questions please

Hello,


I m in the process for preparing for the pmp exam and trying to answer a lot of practice questions.


I need help with the scheduling questions ( Q 42-50) from the sample questions on the site : http://sites.google.com/site/pgmpguide.


I would like some explanation on how the answers were arrived.Anyone arrived at the correct answers, please explain.  Thanks a lot !