Two Variables · Challenge problem

Study hours and quiz scores $(1, 60)$, $(2, 70)$, $(3, 65)$, $(4, 80)$, $(5, 75)$ have $r = 0.8$ and the scores have sample SD $\sqrt{62.5} \approx 7.9$. What is the ratio of the SD of the predicted values $\hat y$ to the SD of the observed $y$?