Please help with these two questions

R18. How long does it take a packet of length 1,000 bytes to propagate over a link of distance 2,500 km, propagation speed 2.5-10 m/s, and transmission rate 2 Mbps? More generally, how long does it take a packet of length L to propa- gate over a link of distance d, propagation speed s, and transmission rate R bps? Does this delay depend on packet length? Does this delay depend on transmission rate? R19. 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 R,-500 kbps, R2 2 Mbps, and R, 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 R, reduced to 100 kbps