FLOW CONTROL closed

Question

Consider three nodes A B, C connected in series. Node A is connected to Node B via 3 Gbps link, 500 km length. Node B is connected to Node C via 60 Mbps link, 15 km length. The links are full duplex, but no other traffic on the links. A large file is to be sent from Node A to Node C. Packets are 1024 bytes. Assume velocity of propagation as $2 \times 10^8$ m/sec. What is the round trip time?______  msec (correct to two decimal points).

Comments

Given ans = 5.23

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please explain your solution

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This is what I followed
There are two links first link between A and B has higher bandwith as compared to the next link . So if we send the packets on the link A-B with its given bandwidth then in that case there would be congestion at node B because it will be receiving the packets at a faster rate than that by which it can send them further to C.
So I have considered the bandwidth of 60Mbps to transfer the packets.
Using this I calculated the transmission time which comes around 0.136 ms at one node . But I m not getting where I am going wrong not getting the exact answer.
Is there any range given in the answer??