The Voltage-length characteristics of a direct current arc in an arc welding process is $V=(100+40l)$ ,where $l$ is the length of arc in $mm$ and $V$ is arc voltages in volts.during a welding process,the arc length varies between $1$ and $2 \: mm$ and welding current is in range $200-250 \: A$.Assuming a linear power source,the short circuit current is_____$A$