There are three Processes P$1,$ P$2$ and P$3$ sharing mailbox A$.$ Process P$1$ sends a message to mailbox A$,$ while P$2$ and P$3$ execute a receive $()$ command from mailbox A$.$

a$)$State three methods that could be used for deciding which process receives the message first.

b$)$What is the issue with a mailbox being owned by a process as opposed to the operating system?