2) (30 points) Consider transmitting a file of size F bits from a host A to a host B. There are four links between A and B with transmission bit rates R, = R bit/s, R2 = 2R bit/s, R3 = 4R bit/s, and R4 = 8R bit/s Each link has a distance (length) of d meters. Let s meters/second denote the propagation speed on the links. Assume that the routers interconnecting the access links and backbone have unlimited buffer capacity and negligible nodal processing delay. There are no other traffic flows in the considered network. a) Suppose message switching is used, i.e., the entire file is treated as one large packet. How long does it take to transmit the file