Two Variables · Challenge problem

Five points $(1, 4)$, $(2, 10)$, $(3, 11)$, $(4, 12)$, $(5, 18)$ have least-squares line $\hat y = 2 + 3x$ and $r^2 = 0.9$. A sixth point is added at $(3, 11)$, which is exactly the point of means. What is the new $r^2$?