$6\mathrm{.}4-4.$ Self Learning Switches $($a$).$ Consider the network below with six nodes, star$-$connected into an Ethernet switch. Suppose that A sends a frame to $A,A^{\text{'}}$ replies to $A,$ then $B$ sends a message to $B^{\text{'}}$ and $B^{\text{'}}$ replies to $B.$ Enter the values that are present in the switch's forwarding table after B$\text{'}-$to$-$B frame is sent and received. Assumed that the table is initially empty and that entries are added to the table sequentially. Answer the questions below from the pulldown list.