Hello this is Mary Helen from Houston.
I chose to answer the first challenge question because this water pump model is the one I studied during the code.org PD.
Here is the URL link : http://www.slnova.org/189071/projects/219665/
What I struggled with the most was understanding how changing the x coordinate would change the placement of the pump. And how changing the x coordinate into the negative position would change the placement of the pump.
I still need help understanding the true placement of the pump. I do not think that I am fully understanding.