Consider sending a file of 50 Mbits over a path of 4 links. Each link transmits at a rate of 10 Mbps. The network is lightly loaded so that there are no queuing delays, the processing delay is negligible, and that the propagation delay on each link is 20 milliseconds. Using these assumptions, answer the following: a. Suppose the network is a packet-switched datagram network, and a connectionless service is used. Suppose that the file is broken into 10,000 packets. Now suppose each packet has 320 bits of header. How long does it take to send the file? b. Repeat (a), but assume message switching is used (i.e., 320 bits are added to the file, and the file is not segmented). c. Finally, suppose that the network is a circuit-switched network. Further, suppose that the data rate of the circuit between source and destination is 10 Mbps. Assuming the circuit is made up of 4 links with a propagation delay on each link being 20 milliseconds, a 500 milliseconds set-up time, and 160 bits of header appended to the entire file, how long does it take to send the file?