According to Kepler's Law of areas, \(v_A < v_P\)
\(v_A=\) speed of planet at aphelion
\(v_P=\) speed of planet at perihelion
Now, work done by gravitational force of sun \(=\Delta K \cdot E=\frac{1}{2} m\left(v_A^2-v_P^2\right)\)
\(\Rightarrow W_{\text {gravitation force }}\) is negative.