Some terms you should know before solving this question
Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a processor.
I/O buses connect the CPU to all other components, except RAM. Data are moved on the buses from one component to another, and data from other components to the CPU and RAM. The I/O buses differ from the system bus in speed.
A bottleneck, in a communications context, is a point in the enterprise where the flow of data is impaired or stopped entirely. Effectively, there isn't enough data handling capacity to handle the current volume of traffic.
Since I/O bus speed is less than Memory bandwidth,it is bottleneck.
Effective bandwidth that the I/O bus can provide is 1000/2 =500Mbps because each packet crosses the I/O bus twice.
Therefore, the number of interfaces is ⌊500/100⌋ = 5
