A hot iron having specific heat \(0.5 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\), mass \(30 \mathrm{~kg}\) and temperature \(500^{\circ} \mathrm{C}\) is dropped into \(200 \mathrm{~kg}\) of oil of specific heat \(2.5 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\). Calculate change in entropy of iron, oil and composite system.