For a), I do not understand why the answer is L/Rs instead of L/Rc. Please help.

2. Consider an end to end path from a server to a client shown as the figure. Assume that the links along the path from the server to the client are the first link with rate Rs bits /sec and the second link with rate Rc bits /sec. Suppose the server sends a pair of packets back to back 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? (2 points) b) Now assume that the second link is the bottleneck link (i.e., Rc