Final answer:
The unit rate of water usage given in the question is 50 cubic feet per minute, which directly answers the question without any further calculation needed.
Step-by-step explanation:
The question asks about the unit rate of water flow in cubic feet per minute. A unit rate is a measure of the amount of one unit with respect to one unit of another measure. In this case, we have water usage of 50 cubic feet per minute. Therefore, the unit rate of water usage is simply the amount of water used in one minute, which is given as 50 cubic feet.
So the unit rate of the water is 50 cubic feet per minute because the question directly tells us that the water usage is 50 cubic feet per minute. Hence, the correct choice is:
b) 50 ft³/min