18,000 @ 192kbps tool up 93gb 
that' pretty much what kpac said- rephrased.
let's see- 93GB/18,000= approximately 5.3 MB for each song.
5.3MB*40,000= 206.66GB
HOWEVER- we must take into account that most music space measurements use 128kbps despite it sucking severely- so reduce the size another third, to around 137GB.
naturally chopping off a third from the bitrate won't translate directly into a third reduction in size, so chances are it will
really be around 160GB for 40,000 songs.
The end.
