There are 4 shapes on a 9x9 grid. Which shape is closest to the green right_triangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: green right_triangle at (8, 3)
Distance from target shape to purple right_triangle at (5, 4): 4
Distance from target shape to blue right_triangle at (1, 7): 11
Distance from target shape to pink right_triangle at (6, 7): 6
Closest shape is the purple right_triangle at (5, 4) with distance 4</think>

<answer>(5, 4)</answer>