determining a total amount of fuel required to raise {HEAD ~ the temperature} of {TAIL ~ exhaust} above a regeneration temperature based on the determined flow rate and the determined temperature; and 
determining a total amount of fuel required to raise { HEAD ~ the temperature } of { TAIL ~ exhaust } above a regeneration temperature based on the determined flow rate and the determined temperature ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH