Suppose two nodes, A and B, ar

Suppose two nodes, A and B, are attached to opposite ends of a 900 m cable, and that they each have one frame of 1000 bits (including all headers and preambles) to send to each other. Both nodes attempt to transmit at time t=0. Suppose there are four repeaters between A and B, each inserting a 20 bit delay.Assume the transmission rate is 10 Mbps, and CSMA/CD with backoff intervals of multiples of 512 bits is used. After the first collision, A draws K=0 and B draws K=1 in the exponential backoff protocol. Ignore the jam signal.
a) What is the one-way propagation delay (including repeater delays) between A and B in seconds. Assume that the signal propragation speed is 2 * 108m/sec.
b) At what time (in seconds) is A's packet completely delivered at B.
c) Now suppose that only A has a packet to send and that the repeaters are replaced with bridges. Suppose that each bridge has a 20 bit processing delay in addition to a store-and-forward delay.At what time in seconds is A's packet delivered at B?