{HEAD ~ the density determination system} is operable to determine {TAIL ~ a first density value} and a second density value of the fluid at the first time and the second time, respectively 
is operable to determine
{ HEAD ~ the density determination system } is operable to determine { TAIL ~ a first density value } and a second density value of the fluid at the first time and the second time , respectively
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH