Answer
$y_1$, $y_4$, $y_2$, $y_3$
Work Step by Step
$$v=\sqrt\frac{\tau}{\mu}$$ $$\tau=\mu v^2$$ If $\mu$ remains constant, as velocity increases, tension increases. Therefore, the order giving wave speed from greatest to least is the same as the list of tension from greatest to least; $y_1$, $y_4$, $y_2$, $y_3$.
