At {HEAD ~ the primary power rate}, a battery may have a life of, for example, {TAIL ~ two hours} 
At { HEAD ~ the primary power rate } , a battery may have a life of , for example , { TAIL ~ two hours }
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL