SQL question

Consider the three transactions T1, T2 and T3, and the schedules S1, S2, S3 and S4 given below. Which of the schedules is (conflict) serializable? The subscript for each database operation in a schedule denotes the transaction number for that operation. For each schedule, show all conflicts, draw the precedence graph, determine and write down if it is serializable or not, and the equivalent serial schedules if exist.

T1: r1(x); w1(x);

T2: r2(x);

T3: r3(x); w3(x);

S1: r1(x); r3(x); w1(x); r2(x); w3(x);

S2: r1(x); r3(x); w3(x); w1(x); r2(x);

S3: r3(x); r2(x); w3(x); r1(x); w1(x);

S4: r3(x); r2(x); r1(x); w3(x); w1(x);