A project has the following risk:

5% probability of an additional acceptance test resulting in 3 weeks delay

50%  probability the next software release will not be ready by the due date resulting in an 8 week delay

30%  probability that a new resource will be available and duration of activity will be reduced by 4 weeks.

 

The answer is 20.65 days, by the below formula

 

(.05 * 21) + (.5 * 56) - (.3 * 28)

 

My question is why 7 days are assumed in a week. I shoudl be 5 days right. I remember it reading it some where that assume 8 hrs a day and 5 days a week in solving numericals