Please need help in this and a proper explanation of the answer as well.

Consider The followig figure.

Assume that we know the bottleneck link along the path from the server to the client is the first link with rate Rs bits/sec. Suppose we send a pair of packets back to back from the server to the client, and there is no other traffic on this path. Assume each packet of size L bits, and both links have the same propagation delay dprop.

a. What is the packet inter-arrival time at the destination? That is, how much time elapses from when the last bit of the first packet arrives until the last bit of the second packet arrives?

Server Client a. RN Server Client 2o Figure 1.19. Throughput for a file transfer from server to client