Bottlenecking occurs when a device in the network (such as an IPS) cannot process traffic efficiently, resulting in a dramatic drop in throughput. The significant difference between the firewall's speed (48.8 Mbps down) and the end-user devices' speeds (4.8 - 5.2 Mbps down) indicates a bottleneck caused by the IPS.
*Why not the other options?
*Packet loss (A) - Would typically cause connection timeouts, not just slow speeds.
*Channel overlap (C) - Affects only wireless networks, but the wired desktop is also experiencing slow speeds.
*Network congestion (D) - Would show fluctuations in both upload and download speeds, but upload speeds remain unaffected.