4. In the figure on the top of the next page, four PCs (with indices 1, 2, 3, and 4) are connected through two bus-topology local area networks (LANs). The address configuration is also shown in the figure, where a capital-case letter means an IP address and a number means a physical address. Any data frame in the network has the following format: Layer 2 header header h eader Layer 2 trailer Layer 3 Layer 4 Layer 4 data Assume a process with port address '' on PC 2 sends a message to a process with port address q'on PC 4. In the following table, please indicate the source & destination addresses used in the header of Layers 2, 3, and 4, for the data frame from PC 2 to the router and the data frame from the router to PC 4. (6 points) A/55 E/66 PC 3 PC1 Router D/44 B/22 PC 4 PC 2 Data frame from PC 2 to the router Source address Destination address Data frame from the router to PC4 Source address Destinati Layer 2 header Layer 3 header Layer 4 header