Parent State ID: 51
State Depth: 10
Action Taken: stack(b, a)
Action Reasoning: To achieve the goal state, block 'b' should be placed on block 'a'. Since the hand is currently holding block 'b', the best action is to stack 'b' on '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.
Action Path: ['unstack(c, d)', 'put-down(c)', 'unstack(d, a)', 'stack(d, b)', 'pick-up(c)', 'put-down(c)', 'pick-up(a)', 'stack(a, c)', 'pick-up(b)', 'stack(b, a)']
