Consider an $n$-channel MOSFET having width $W$, length $L$, electron mobility in the channel $\mu _{n}$ and oxide capacitance per unit area $C_{ox}$. If gate-to-source $V_{GS}=0.7$ V, drain-to-source voltage $V_{DS}=0.1 V$, $\mu _{n}C_{ox}=100 \mu A/V^{2}$, threshold voltage $V_{TH}=0.3V$ and $(W/L)=50$, then the transconductance $g_{m}$ (in mA/V) is __________.