Parent State ID: 39
State Depth: 9
Action Taken: unstack(d, b)
Action Reasoning: To achieve the goal state, we need to move block 'a' onto block 'b'. First, we need to clear block 'b' by moving block 'd' to the table.
State Description: The hand is holding block 'd'. Block 'b' is now clear and on the table. Block 'a' is on block 'c' and is clear. Block 'c' is supporting block 'a' and is no longer clear.
Action Path: ['unstack(c, d)', 'put-down(c)', 'unstack(d, a)', 'stack(d, b)', 'pick-up(a)', 'stack(a, c)', 'unstack(d, b)', 'stack(d, b)', 'unstack(d, b)']

INACTIVE REASON: deactivated because diagram generation failed or invalid action chosen: Action moves 'd' away from 'b', contrary to the goal state.
