Digital BW, The Print

question from not a photo newbie but a B&W newbie...Why can't you just 
take out the 5 color cartriges and leave in just the 3 black ones to 
guarantee yourself no color cast in the R2400?  and why does the 
advertisement on the R2400 say 9 ink cartrages?  can you really have 9 
ink cartriges all going at once?  if so, can you have 4 black cartriges 
and leave out the 5 color ones?

thanks for helping 
Eddie