In the figure, transistors $T_1$ and $T_2$ have identical characteristics. $V_{CE(sat)}$ of transistor $T_3$ is $0.1\:V$. The voltage $V_1$ is high enough to put $T_3$ in saturation. Voltage $V_{BE}$ of transistors $T_1,T_2$ and $T_3$ is $0.7 V$. The value of $(V_1-V_2)$ in $V$ is _________________.
