4. Consider the BJT cascade amplifier shown below Vcc 18V R1 3.3ko 15uF r Vo RL B 150 Rsa 500? 56k? Vi B 150 C1 CE 2.2k? a) Find the DC collector current (approximately the same in both transistors). b) Find the input impedance, output impedance, and no-load voltage gain. c) Find the Av, Avs, and Ai d) Estimate the lower cutoff frequency e) Why does this amplifier have better high-frequency performance thana common-emitter built using the same type of transistor and using the same bias point?