Consider the schedule S1 consists of three transactions T1, T2, T3 as the following: T1 R(B) R(D) Commit S1 T2 R(B) W(B) R(D) commit T3 R(A) R(C) commit Answer the following question: a) Is the schedule S1 cascadeless and recoverable? Justify your answer. b) Draw the precedence graph of schedule S1 c) Is S1 conflict-serializable? Explain briefly. If S1 is conflict-serializable, write down all equivalent serial schedules.