Assume a protocol stack has 5 layers, with the topmost layer being the application layer. The four lower layers each adds an overhead of 30 bytes as headers and trailers, and does not change the packet payload. Consider the application layer sending application PDUs with different sizes as follows. Compute the percentage bit overhead in this stack as seen over a long period of communications. Use the application layer PDU as the basis. A. Application sends 200-byte fixed-length PDUs at all times. B. Application sends 200-byte PDUs at half of the times, and 400-byte PDUs at the other half. C. What might be the reason that we do not want to have very large PDU sizes (e.g., 1MB data per packet) to make the overhead of layering as low as possible