\begin{table}%t2
\caption{Errors in the shock tube problems~3 and~6 for HLLE and
Roe's approximate Riemann solvers, and Tadmor's central scheme using 
two different third order spatial reconstructions (CFL~$=$ 0.5 and $N_x=400$).}\label{errors}
%\centering
\par
\begin{tabular}{cccccc}
\hline  \hline
Test & Scheme & \multicolumn{2}{c} {$L_1$ ($10^{-2}$)} & \multicolumn{2}{c} {$L_{\infty}$ ($10^{-3}$)} \\
 \hline
&  & PPM & PHM & PPM & PHM \\
 \hline
Problem 3 &  HLLE & 3.37 & 2.81 & 2.87 & 0.67 \\
&  Roe & 3.39 & 2.95 & 3.44 & 1.31 \\
&  Tadmor  & 3.41 & 3.41 & 2.58 & 1.04 \\
  \hline
Problem 6 &  HLLE & 22.0 & 21.7 & 3.53 & 1.20 \\
&  Roe & 21.7 & 21.6 & 2.63 & 1.20 \\
&  Tadmor  & 25.2 & 22.4 & 0.92 & 2.69 \\
  \hline
\end{tabular}
\end{table}