Iteration 2

 

The LP at level 1 includes the lower bound restriction on X6. Not surprisingly the LP objective decreases. The variable with the largest fractional value is X5. Since its value is closer to 0 than 1, we choose to branch down by placing an upper bound of 0 on X5. With upper and lower bounds both at 0, X5 will be forced to 0 in the next relaxed LP.
LP

Tree
Action