If the cost is impossible to determine, {HEAD ~ use} of cost per unit to minimize {TAIL ~ the number} of hops may be useful 
to minimize
If the cost is impossible to determine , { HEAD ~ use } of cost per unit to minimize { TAIL ~ the number } of hops may be useful
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH