A river is flowing from west to east direction with speed of \( 9 \, \text{km h}^{-1} \). If a boat capable of moving at a maximum speed of \( 27 \, \text{km h}^{-1} \) in still water, crosses the river in half a minute, while moving with maximum speed at an angle of \( 150^\circ \) to direction of river flow, then the width of the river is:
