A message of size 3000 bytes is broken up into 2 equal size data packets and sent from node A to C in the network shown below, in a pipelined manner, after adding a header of size 40 bytes to each packet. Node C acknowledges every packet received, and each acknowledgement packet has a size of 40 bytes. Assume store-and-forward switching, speed of light = 2108 m/s, no losses or errors, and queuing and processing delays are negligible (transmission and propagation delays must be considered, however). Further assume that links are full duplex, i.e., data can be sent in both directions on a link at the same time. 100 Mbps 20 Mbps A B 1 km 10 km If node A starts transmitting the first packet at time t=0, calculate the time at which node A receives the acknowledgement for the second packet.