For the closed loop amplifier circuit shown below, the magnitude of open loop low frequency small signal voltage gain is $40$. All the transistors are biased in saturation. The current source $I_{S S}$ is ideal. Neglect body effect, channel length modulation and intrinsic device capacitances. The closed loop low frequency small signal voltage gain $\frac{v_{\text {out }}}{v_{\text {in }}}$ (rounded off to three decimal places) is $\_\_\_\_\_\_$.
- $0.976$
- $1.000$
- $1.025$
- $0.488$