$${W_T = m \left( - \frac{g}{5} + g \right) d\, \cos \phi = \frac{4}{5} mgd\, \cos \phi \\ = \frac{4}{5} (500\, \mathrm{kg})(9,8\, \mathrm{m/s^2})(12\, \mathrm{m}) \cos 180^{\circ} \\ = -4,70 \times 10^4\, \mathrm{J} \approx \underline{\underline{-47\, \mathrm{kJ}}}}$$