Suppose that 2PC with Presumed Abort is used as the commit protocol. Explain how the system recovers from failure and deals with particular transaction T in each of the following cases: (a) A subordinate site for T fails before receiving a prepare message. (b) A subordinate site for T fails after receiving a prepare message but before making a decision (c) The coordinator site for T fails before sending a prepare message, (d) The coordinator site for T fails after writing an abort log record but before sending any further messages to its subordinates.