13. (3+2+3 points) The following figures plot the timeline for sending TCP segments by host A and TCP ACKS by host B, where seq # is the value of the sequence number in the TCP header, and "ACK #" is the value of the acknowledge number in the TCP header. Assume that every segment always includes 500 bytes of data, excluding the TCP header. A seg #: 1008 seq #: 1500 seq #: 2000 seq #: 2500 (1) B ACK #: a ACK #: b ACK #: c ACK #: d A #: seq 1008 seq #: 1500 seg #: 2000 seq #: 2500 (2) B ACK#: r ACK #: s ACK #: t 1) In Figure (1), the second ACK sent out by host B gets lost in the network. a) What are the acknowledge numbers a, b, c, and d? b) Will sender A think the segment with seq#=1500 was lost because it never receives the acknowledgement from B containing ACK# = b? 2) In Figure (2), the second TCP segment from host A to host B gets delayed in the network but later arrives at B. What should be the value for the ACK number r, s and t?