For denominator, start from root node, visit every node and multiply the result with number of nodes present in that subtree.

Eg here for root node :- subtree has 9 nodes,

For left child of root :- subtree has 5 nodes,

For right child of root :- subtree has 3 nodes...

So on calculate for every node to obtain denominator.

You will get 9x5x3x3x1x1x1x1x1

Now Why are they doing this?