calculating a certain write power Pth for which {TAIL ~ the modulation index} is zero by using {HEAD ~ the optimum write power compensated value PcO}; and 
calculating a certain write power Pth for which { TAIL ~ the modulation index } is zero by using { HEAD ~ the optimum write power compensated value PcO } ; and
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH