Consider the following schedules S1 and S2 by transactions T1, T2 and T3 on database objects A and B.

S1 : R1(A), R3(B), W1(B), R2(B), W3(A), W1(A), R3(A)

S2 : W1(A), R1(B), W2(B), W1(B), R2(A), W3(B), R3(A)

(a) Determine if schedules S1 and S2 are conflict-serializable by drawing a precedence graph of transactions. (2+2 = 4 points)

(b) For the same schedules S1 and S2, determine if they are serializable. If serializable, then give a corresponding serial schedule. If not serializable, provide a suitable justification. (2+2 = 4 points)