$v \propto \frac{{\sqrt T }}{r} $
$\Rightarrow \frac{{{v_A}}}{{{v_B}}} = \sqrt {\frac{{{T_A}}}{{{T_B}}}} .\frac{{{r_B}}}{{{r_A}}} = \sqrt {\frac{1}{2}} .\frac{1}{2} = \frac{1}{{2\sqrt 2 }}$
$(a)$ $\left(x^2-v t\right)^2$
$(b)$ $\log \left[\frac{(x+v t)}{x_0}\right]$
$(c)$ $e^{\left\{-\frac{(x+v t)}{x_0}\right\}^2}$
$(d)$ $\frac{1}{x+v t}$