two hosts, a and b, are separated by 20,000 kilometers and are connected by a direct link of 1 mbps. the signal propagation speed over the link is 2.5 × 108 meters/sec. a. what are the one-way propagation delay and round-trip time? b. calculate the bandwidth-delay product, ???????? ⋅ ????????prop. c. what is the bit time? d. what is the maximum number of bits on the link at any given time if a sufficiently large message is sent? e. what is the width (in meters) of a bit in the link? f. derive a general expression for the width of a bit in terms of the propagation speed ????????, the transmission rate ????????, and the length of the link mm.