**My Question:**

*1- How this logic works for this the circuit. Actually I want to calculate the Voltages across transistors. How to calculate those voltages. Can someone please explains me..*

Means Accross T1 ,T2 T3, and T4 and for cases when X1,X2 is 0,0 --- 0,1-----1,1

Means Accross T1 ,T2 T3, and T4 and for cases when X1,X2 is 0,0 --- 0,1-----1,1