Current State ID: 51
Current State Description: The hand is now holding block 'b'. Block 'a' remains on block 'c', and block 'd' is on the table and clear. Block 'b' is no longer on the table.

Child State ID: 59
Action Taken: stack(b, a)
State Description: The hand is now empty. Block 'b' is on block 'a', and block 'a' is on block 'c'. Block 'd' remains on the table and clear. The diagram would show block 'b' stacked on block 'a', forming a tower with 'c' at the base.

