A homogeneous bar of $1\,kg$ in mass is at equilibrium and supported by two wires labeled $A$ and $B$ as shown in the graph. Find the maximum value of the mass in kilograms of the block such that the system remains at equilibrium.

The alternatives given in my book are as follows:

$\begin{array}{ll}

1.&3\,kg\\

2.&4\,kg\\

3.&6\,kg\\

4.&30\,kg\\

\end{array}$

What I've attempted to do was to establish the torque about the end on B. But I end up with two unknowns for the mass and for the tension. How can I get the mass?.