The time it takes to lift 50 15.0-kg boxes at 41.4 W output will depend on several factors such as the height the boxes need to be lifted, the efficiency of the lifting mechanism, and the strength and speed of the person lifting the boxes. Without these variables, it is impossible to accurately determine the time it will take.
It is possible for a person to lift 50 15.0-kg boxes at 41.4 W output, but it may not be safe or practical to do so. The weight of the boxes and the output needed would require a significant amount of strength and endurance from the person lifting the boxes.
The amount of power needed to lift 50 15.0-kg boxes will depend on the height the boxes need to be lifted and the speed at which they need to be lifted. The 41.4 W output mentioned in the question may not be enough to lift the boxes, as it only refers to the rate of doing work and does not take into account the force needed to lift the boxes.
The output can be increased to lift the boxes faster, but it may also require a higher level of strength and endurance from the person lifting the boxes. Alternatively, a more efficient lifting mechanism could also help increase the speed at which the boxes are lifted.
The lifting process can be made more efficient by using a more efficient lifting mechanism, such as a pulley system or a forklift. Additionally, breaking down the boxes into smaller loads or using multiple people to lift the boxes could also increase efficiency and reduce the strain on the person or people doing the lifting.