1600kg has weight (force) of 1600×9.81=15696 Newtons.
(1) Work done=15696×25=392400 joules (force times distance).
(2) Efficiency=output/input=0.6. The output in this case is the work done from (1) (the winch must be capable of lifting the weight). This means that the input has to be higher to compensate for the loss of power because of friction, etc. So input=392400/0.6=654000 joules.
(3) kW=J/(1000t) where J is the work done in joules and t the time in seconds, so kW=654000/30000=21.8kW. The power is this multiplied by t as a fraction of an hour: 30/3600=0.1817kWh approx. Note that joules can be converted directly into kWh by dividing by 1000: 654 kWh.