A parabola with equation $y=k{x}^2+mx+n$ is reflected about the line $y=1$. The parabola is translated horizontally three units to the left to become the graph of $y=f(x)$, and its reflection is translated horizontally three units to the right to become the graph of $y=g(x)$. Which of the following describes the graph of $y=(f+g)(x)$?