Answer:
Et = 30018 [W]
Step-by-step explanation:
To solve this problem we must use the definition of potential energy, which is expressed by the following equation:

where:
Ep = potencial energy [W]
g = gravity acceleration [m/s^2]
h = elevation = 120 [m]
m = mass flow = [1800/min]
But in order to get watts into potential energy, we must convert the mass flow from kilograms per minute to kilograms per second.
![1800[(kg)/(min) ]*(1)/(60)(min)/(s)=30[(kg)/(s) ]](https://img.qammunity.org/2021/formulas/physics/college/xhe5z6xxxjesywrzucm4wey75dzxo1dtwz.png)
Ep = 30*9.81*120
Ep = 35316 [W]
If we use 85% of the potential energy will have:
Et = 35316*0.85
Et = 30018 [W]