9.4 Considering a small network of four hosts and three links as depicted in the figure below. A 1,024,000 bits message is to be sent from A to D. The data rate of the first two links is 0.4 MB/second, but the link between C and D is 1.6 MB/sec. Propagation delays of the links are negligible. A B C D a. Assume that circuit switching is used and the total circuit set-up time is 100 ms, what is the time to send the message from A to D? b. Assume that message switching is used and queuing delays are negligible, what is the time to send the message from A to D? c. Assume that packet switching is used, packet size is 128 bytes and header size is 22 bytes (128 bytes is only payload, excluding header), what is the time to send the message from A to D? Hint: throughput of a pipeline is decided by how long it will take to pass the bottleneck step