Knowing I5, I1, I2, you can calculate Vgs5, Vgs1 and Vgs2. From that you can calculate input common mode voltage Vin and Vbias.

Vdrain = VDS5+vddTo find Vin-
VDS5 = Vdrain- Vdd--> Vdrain= VDS5-vdd
Vdrain = Vs1
Vin+ = Vdrain - Vsg1
Thank you.Vdrain = VDS5+vdd
For input common mode voltage Vcm = Vin+ = Vin- = Vdd - Vsd5 - Vsg1.
(Vsg1 = Vsg2)
Yes, it is OK.Thank you.
So is my equation for Vbias correct as well?