Attempt Number: 4
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
To align with the goal state, we should stack block 'b' on block 'a', as 'a' is already on 'c', and this will bring us closer to the desired configuration.

New State Description:
The hand is now empty. Block 'b' is on block 'a', which is on block 'c', achieving part of the goal state. Block 'd' remains on the table and clear.

Action Chosen:
stack(b, a)
