4.(30%) Figure 3 shows the common-source amplifer with an ideal current source I = 0.4 mA, 62f5dfbce1b67.jpg= 200 kΩ, RG = 2 MΩ, RD =RL = 20 kΩ, C1 = C2 = C3 = 1 HF. The MOSFET has the device parameters: I = 0.2 μm, W = 2 μm, 62f5e030d9386.jpg = 10 fP/μm2, μn = 450 cm2/V-s, r0 = 100 kΩ, 62f5e07de1bd0.jpg = 3.2 fF, 62f5e09deddd2.jpg can be neglected, and the source terminal of MOSFET is connected to its body terminal. Please calculate (1) the transconductance gm of the MOSFET, (2) the AM  f1,f2,f3 (let f1 <f2<f3) values of the overall low- frequency transfer function 62f5e152c4c28.jpg, (3) the upper 3-dB frequency fr by using open-circuit time constants method. (5%, 5%*4, 5%)