Below is the linear programming for the Shortest Path Problem. Considering the second contraint in the mathematical model :
∑ixji−∑ixij=0∀j≠s, j≠t
What is the logic behind this contraint?
A. To make sure there is only one solution
B. To make sure that the path is connected between the nodes
C. To make sure the variable stays binary
D. This contraint is redundant and not necessary

Using pert, adam munson was able to determine that the expected project completion time for the construction of a pleasure yacht is 21 months, and the project variance is 4. a) what is the probability that the project will be completed in 17 months? b) what is the probability that the project will be completed in 20 months? c) what is the probability that the project will be completed in 23 months? d) what is the probability that the project will be completed in 25 months? e) what is the due date that yields a 95% chance of completion?