How to calculate number of nodes opened by BFS?

Question

In the below diagram, each node takes up a space of 2KB. I need to find the total memory consumed to reach the goal : I

I know that the equation for BFS is

b¹ + b² + ...... + (b^d+1 - b)

Where b is the branching factor and d the depth

But how do I calculate the branching factor in the below diagram, where the branches are uneven?

Also, is the depth on A node 0 or 1?