Calculate maximum ammount of Bus Bandwidth Don't know if this is the right community for this and this should be pretty basic but here goes.
I'm studying System Engineering and one of the homework problems is the following question.


  A 32-bit computer with a 200-MHZ Bus requires four cycles to read a
  32-bit word. How much bus bandwidth does the CPU consume in the worst
  case ?


I just can't get my head around this for some reason.
I thought that because it's a worst case scenario the CPU would just consume 4x (cycle) the entire Bus (200MHZ) which would be 800MB/s. I even reasoned this with reversing BIT > BYTE. Byte per Clock cycle. clock Cycle * Clock rate = bandwidth. 
But appereantly i'm wrong with the correct answer seemingly being 400MB/s. I can't find (in the study material atleast) how to determine this.

Anyone out there that can help me out or at least set me on the right track ?
I could drop this question but i'm afraid this will haunt me in my nightmares.

Thanks so much.
Start from the definition.  Bandwidth is defined as data transferred per unit time.  For instance, it's the number of bytes transferred, per second.

So, work out how many bytes it would be possible to transfer across the bus, in one second.  Forget formulas: just try to reason it through.  How many 32-bit words could you transfer in one second?  How many bytes does that correspond to?