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