Atown is exploring the option of generating hydroelectric power from a stream. what is the maximum available power in a waterfall that has a flow rate of 200 kg/s dropping over a 15 m change in height?

The power is equal to energy transferred per unit time.
So, here power will be due to potential energy of the water kept at a certain height. And water is flowing down at the given flow rate.

The flow rate of water is 200kg/s
And the height given is : 15m

So, we calculate the potential energy as: mgh
Where m is the mass,
g is acc due to gravity = 9.8m/s
h is the height

So, potential energy = 200kg*9.8*15
= 29,400 J

Therefore, the maximum power generated is 29400 J/sec = 29400 Watts