{HEAD ~ The “cost} of survivability” is defined as {TAIL ~ the ratio} of the costs of network operation with and without survivability requirements 
is defined as
{ HEAD ~ The “ cost } of survivability ” is defined as { TAIL ~ the ratio } of the costs of network operation with and without survivability requirements
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH