Parent State ID: 6
State Depth: 4
Action Taken: stack(a, b)
Action Reasoning: To achieve the goal state, we need to place block 'a' on block 'b'. Since the hand is already holding block 'a' and block 'b' is clear, the best action is to stack 'a' on 'b'.
State Description: Block a is on top of block b. Block c is clear and on top of block b. Block b is on the table with block a on top of it. Block d is on the table and clear. The hand is empty.
Action Path: ['unstack(d, a)', 'put-down(d)', 'unstack(a, c)', 'stack(a, b)']
