\begin{table}%t3
\caption{\label{t3}Mean number of predicted thin disk WDs with $B-V<0.35$ and $V<23$,
for different combinations of IMF (exponent $\alpha$) and SFR (constant in
the indicated interval). Results for a thin disk scale height $H=250$ pc and
$H=300$ pc are shown.}
\par
%\centering
\par
\begin{tabular}{ccccc}
\hline\hline
&& $H=250$ pc&\\
$\alpha$     & $N$({\it SFR} 0--6 Gyr) & $N$({\it SFR} 0--4 Gyr) & $N$({\it SFR} 0--2 Gyr) \\
\hline
1.8          &   26     &         37      &            51\\
2.3          &   12      &         13     &            23\\
2.7          &   8       &         11     &            13\\ \hline 
&&$H=300$ pc&\\
$\alpha$     & $N$({\it SFR} 0--6 Gyr) & $N$({\it SFR} 0--4 Gyr) & $N$({\it SFR} 0--2 Gyr) \\
\hline
1.8          &   40      &         53      &            77\\
2.3          &   22      &         23      &            31\\
2.7          &   13       &      15      &      19\\  
\hline
\end{tabular} 
\end{table}