Suppose host a wants to send a large file to host b. the path from host a to host b has three links, of rates r1 = 500 kbps, r2 = 2 mbps, and r3 = 1 mbps. a. assuming no other traffic in the network, what is the throughput for the file transfer? b. suppose the file is 4 million bytes. dividing the file size by the throughput, roughly how long will it take to transfer the file to host b? c. repeat (a) and (b), but now with r2 reduced to 100 kbps.