a)  Assume that the time required to transmit one packet (i.e. the packet length divided by link data rate) is 10ms and the Round Trip Time (from Source to Destination and back) is 50ms. In the space below, draw a diagram illustrating the timing of Source and Destination exchanging packets and acknowledgments using a stop-and-wait protocol. Assume that packets are only sent from source to destination and that acknowledgments (of negligibly small size) are sent back immediately after the data frame is received.  

b)  Calculate link utilisation (proportion of time the channel is actually used for transmission) for the stop-and-wait case.