To prevent inconsistencies when transferring money between two bank accounts, Ai and Aj, the system needs to lock both accounts prior to performing the transfer, then unlock both accounts after the transfer: lock(Ai) and lock(Aj) in either order; update Ai and update Aj in either order; unlock Ai and unlock Aj in either order. (a) Show how a deadlock can occur when multiple transactions are performed concurrently. (b) How could an ordered resource policy be implemented to prevent deadlock?