http://artint.info/2e/html/ArtInt2e.html This is the book for reference

Q1
For the scheduling problem given, the problem statement is:
T1 is reaching the Burnaby campus on {M,Tu,W,Th,F}
C1 is reaching the class in 90 minutes and is the first constraint, a time constraint
C2 is reaching the class before 9:00 am, another time constraint
T1 must occur before T2
Since the class duration is not given, the following domain is based on optimum value of class ending time
Dom(class_time) = {9,10,11,12,1,2,3,4,5}
There is day of class domain:
Dom(class_day) = {M,Tu,W,Th,F}
Variables: X1, X2
X1: reaching class in 90 minutes {true, false}
X2: reaching class before 9:00 am {true, false}
The number of possible worlds are:
1) Reaching class late with X2 as false, reaching class in above 90 minutes X1 as false
2) Reaching class early with X1 as true, reaching class in above 90 minutes X1 as false
3) Reaching class early with X1 as true, reaching class in under 90 minutes X1 as true
4) Reaching class late with X1 as false, reaching class in under 90 minutes X1 as...