A simply supported beam of span 4 m subjected to two-point loads of 60 kN and 40 kN at a distance of 1 m from either supports respectively. An equivalent beam of the same span subjected to 50 kN load at the mid span which produces a vertical deflection of 40 mm and 60 mm at distance of 1 m from either supports. Determine the deflection under the load of 50 kN.