consider two hosts X and Y that are directly connected by a communication link with the following parameters: distance d=2500 kilometers, propagation speed s = 2.510^8 m/s and transmission rate is R=40 Mbit/second. a. how long is the propagation delay in seconds? b. how large is the bandwidth delay product of the communication link? c. how large is the end to end delay (transmission delay plus progagation delay) for transmitting a file with F=4,000,000 bits from X to Y?