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