In the CMOS inverter circuit shown, if the transconductance parameters of the NMOS and PMOS transistors are $k_{n}=k_{p}=\mu_{n} C_{o x} \dfrac{W_{n}}{L_{n}}=\mu_{p} C_{o x} \dfrac{W_{p}}{L_{p}}=40 \; \mu \mathrm{A} / \mathrm{V}^{2}$ and their threshold voltages are $V_{T H n}=\left|V_{T H p}\right|=1 \mathrm{~V},$ the current $I$ is
- $0 \mathrm{~A}$
- $25 \; \mu \mathrm{A}$
- $45 \; \mu \mathrm{A}$
- $90 \; \mu \mathrm{A}$