Q$4)[2$ pts$]$ The Alternating$-$Bit protocol is used to transfer a sequence of two data frames labelled A and $B.$ Assume that the propagation delay $($signal travelling time$)$ in one direction is one time unit, the time to transmit each data frame and the acknowledgment frames is negligible, and the retransmission timers are set for $3$ time units. Draw the sequence diagram for the scenario when data the sequence bit starts at $0$ and the acknowledgment with sequence bit $1$ is lost once. Draw the diagram to scale and indicate the actions for each host on the diagram $($eg: frames are dropped, delivered, etc.$).$ At what time is the last frame $B$ delivered at the destination?