Find Dual of Binary LP

[faek]

Hi all,

I want to find the dual of this linear program :
[tex]\left\{\begin{array}{ll}
min &\quad \sum_{r \in 1..n} c_r x_r \\
s.t &\quad \sum_{r \in 1..n} x_r \geq k \\
&\quad x_r \in \{0,1\}
\end{array}\right.[/tex]
and how we can find a dual problem from binary LP ?

Thank's and regards

faek