Consider sending a file of 60 Mbits over a path of 4 links. Each link transmits at a rate of 2 Mbps. The network is lightly loaded so that there are no queuing delays. Assume that the processing delayat each node is 1 millisecond, and that the propagation delayon 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 15,000 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 thefile, and the file is not segmented).

c.Finally, suppose that the network is a circuit-switched network. Further, suppose that the transmission rate of the circuit between source and destination is 2 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?