157 -- The figure below shows the velocity--time graph of a particle moving along the X-axis. The average velocity in the direction opposite to the direction of motion, in meters per second, is: [Figure: velocity-time graph with $V(\frac{\text{m}}{\text{s}})$ on vertical axis and $t(\text{s})$ on horizontal axis. The graph starts at $V = 6$ m/s at $t = 0$, decreases linearly to $V = -12$ m/s, then increases back, crossing zero at $t = 20$ s.]
[(1)] zero
[(2)] 6
[(3)] 8
[(4)] 9
\textbf{157 --} The figure below shows the velocity--time graph of a particle moving along the X-axis. The average velocity in the direction opposite to the direction of motion, in meters per second, is:
\textit{[Figure: velocity-time graph with $V(\frac{\text{m}}{\text{s}})$ on vertical axis and $t(\text{s})$ on horizontal axis. The graph starts at $V = 6$ m/s at $t = 0$, decreases linearly to $V = -12$ m/s, then increases back, crossing zero at $t = 20$ s.]}
\begin{itemize}
\item[(1)] zero
\item[(2)] 6
\item[(3)] 8
\item[(4)] 9
\end{itemize}