Distributed database Draw wait for graph for following history. Is following history conflict serialize-able?

Distributed database

Draw wait for graph for following history. Is following history conflict serialize-able? If yes then give an equivalent serial history.

a. RI (X) WI(X) RI (Y) W3(X) W2(Y) R2(X) W2(Z) R4(Z) R4(Y) W4(Y) Cl C2 C3 C4

b. R2(A) RI(B) W2(A) R2(B) R3(A) WI(B) W3(A) W2(B) C2 Cl C3