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