Calculate the differential input impedance - calculate cmrr

Question

I would like to have at least four hours to understand and rewrite the results into a proper paper with my own words. That also means that there is no need for you to put effort into making the paper appear professional and appealing, just intelligible

The circuit to be analysed can be seen in figure 1.

Figure 1 - A differential amplifier with npn transistors

Values for certain elements are as following:

Element	Value
R1	301 kΩ
R2	301 kΩ
R3	1153Ω
R4	1071Ω
V's	12 V
V'eg	12 V
I	1.35 mA
REE	57 kΩ

r_o can be ignored. β can be set to 100 when analysing small-signal for both transistors.

I assume that V_pos and V_neg are intended to be DC voltages only, since they function as a V_CC , but it is not mentioned anywhere in the paper, so it's purely an assumption I've made.

Task #1:

Calculate Av = v_out/v_id.

I have dealt with differential transistors once in a previous semester, but not like the one shown in figure 1. So far when I've had to engage these problems, I've been able to find the various currents by analysing in the opposite direction of the current source I (since I know that, when both sides are similar, 1/2 I = IEQ₁ = IEQ₂). Now that the resistance R₄ is only applied on one side, and R₃ connects the two transistors, I'm not so sure if that method is acceptable.

Task #2:

Calculate the differential input impedance R_id.

If at this point you feel like you've spent more time than what is fair relative to what I'm paying, and it's not later than 12 a.m. CET (UTC/GMT +1), I can accept it. At least that way I'll be able to look into it myself.

Task #3:

Calculate CMRR when the internal resistance of the current source is set to R_EE?