A 3.50 kN piano is lifted by 3 workers at constant speed to an apartment 25 m above ground. Each worker is able to deliver 165 W of power and the pulley is 75% efficient (25% lost due to friction on pulley). Neglecting mass of pulley, what is the time required to lift the piano from the street to the apartment. I know that F=T-mg=ma=0 T=3500N Work=3*165=495W=F/t But I'm not really sure how to sort this problem out and incorporate the 75% efficiency of the pulley and the height above ground. Please help me.