\(\left.E_{\text {mech. }}=8\right]\)

\((A)\) at \(x\,>\,x_{4}, \quad U=\) constant \(\left.=6\right]\)

\({K}={E}_{{mech} .}-{U}=2\, {J}=\) constant

\((B)\) at \(x\,<\,x_{1}, \quad U=\) constant \(\left.=8\right]\)

\({K}={E}_{\text {mech. }}-{U}=8-8=0 \,{J}\)

Particle is at rest.

\((C)\) At \(x=x_{2}, U=0 \Rightarrow E_{\text {mech. }}=K=8\) ]

\({KE}\) is greatest, and particle is moving at fastest speed.

\((C)\) \((D)\) At \(\left.x=x_{3}, \quad U=4\right]\)

\({U}+{K} =8\, {J}\)

\({K} =4\, {J}\)