Suppose the values $10, -4, 15, 30, 20, 5, 60, 19$ are inserted in that order into an initially empty binary search tree. Let $T$ be the resulting binary search tree. The number of edges in the path from the node containing 19 to the root node of $T$ is ________ . (Answer in integer)

Let us trace the insertions into the binary search tree (BST):

1. Insert 10: Root of the tree.

2. Insert -4: Since $-4 < 10$, it becomes the left child of 10.

3. Insert 15: Since $15 > 10$, it becomes the right child of 10.

4. Insert 30: $30 > 10 \implies$ right of 10; $30 > 15 \implies$ right child of 15.

5. Insert 20: $20 > 10 \implies$ right of 10; $20 > 15 \implies$ right of 15; $20 < 30 \implies$ left child of 30.

6. Insert 5: $5 < 10 \implies$ left of 10; $5 > -4 \implies$ right child of -4.

7. Insert 60: $60 > 10 \implies 60 > 15 \implies 60 > 30 \implies$ right child of 30.

8. Insert 19: $19 > 10 \implies 19 > 15 \implies 19 < 30 \implies 19 < 20 \implies$ left child of 20.

The path from the root node (10) to the node containing 19 is:

The edges on this path are:

1. $(10, 15)$

2. $(15, 30)$

3. $(30, 20)$

4. $(20, 19)$

Therefore, the number of edges is 4.