Current State ID: 4
Current State Description: Block 'a' is now on the table and clear. The hand is empty. Block 'd' remains clear and on block 'b'. Block 'b' is supporting block 'd' and on block 'c'. Block 'c' is on the table, supporting block 'b'.

Child State ID: 6
Action Taken: unstack(block_d, block_b)
State Description: Block 'a' is on the table and clear. The hand is holding block 'd'. Block 'b' is clear and on block 'c'. Block 'c' is on the table, supporting block 'b'. The hand is not empty.

