Consider two hosts A and B located 20,000Km apart. The end-to-end path between them is not congested and crosses one switch S. All the links along the path have a speed of 1.5Mbps. Consider the transfer of a 64Kilobyte file from A to B and assume that each network packet is mapped to a link layer frame that has 32 additional bytes of header. The switch uses store and forward and spends 10us processing each frame. Also, assume the speed of propagation to be 2 x 105Km/s. Answer the following: a. Give the definition of the propagation delay then calculate the propagation delay from A to B, and assuming symmetric links deduce the round-trip time (RTT). b. Assuming the whole file is sent in one packet (message switching), what is the total time required to move the file from A to B c. Assuming that the network layer limits the packet size to 2KByte each and that the packets are sent back-to-back, what is the total time to move the whole file from A to B?