Solution
= Solution
The shock speed is
$$
V_s=\dot R=\frac{C}{3}t^{-2/3}=\frac{R}{3t}.
$$
Apply the <Strong-shock Rankine-Hugoniot conditions> in the shock frame and transform the downstream velocity back to the ambient-medium frame. With the <shock compression ratio>
$$
\chi=\frac{\gamma+1}{\gamma-1},
$$
the post-shock values are
$$
\boxed{
\rho_{\rm ps}=\chi\rho_0,
\qquad
u_{\rm ps}=\frac{2}{\gamma+1}V_s,
\qquad
p_{\rm ps}=\frac{2}{\gamma+1}\rho_0V_s^2}.
$$