A kN piano is lifted by three workers at constant speed to an apartment m above the street using a pulley system fastened to the roof of the building. Each worker is able to deliver W of power, and the pulley system is % efficient (so that 25.0% of the mechanical energy is transformed to other forms due to friction in the pulley). Neglecting the mass of the pulley, find the time required to lift the piano from the street to the apartment