The standard form of a circle is

where h and k are the center and x and y are the coordinates you're given. We need to solve for the radius to finish this off correctly. Filling in, we have

and

, giving us that

. Therefore, our equation is
The formula of a function is the rise over run.
The slope would be 2/5.
Hope this helps!
The correct answer is the 2nd choice because -1/6 is closer to 0 and the surface of the pool would be considered 0. -4/6 is farther away from 0 so it is less.