An $\text{npn}$ transistor under forward-active mode of operation is biased at ${I}_{C} =1 \mathrm{~mA}$, and has a total emitter-base capacitance $\mathrm{C}_{K}$ of $12 \; \mathrm{pF}$, and the base transit time $\tau_{F}$ of $260 \; \mathrm{psec}$. Under this condition, the depetion capacitance of the emitter-base junction is ___________ [use $V_{T}=26 \; \mathrm{mV}$ ]