in step {HEAD ~ each} of {TAIL ~ the third cooktop units} is preassmbled with a respective single cooking system type prior to mounting on the base units 
of
in step { HEAD ~ each } of { TAIL ~ the third cooktop units } is preassmbled with a respective single cooking system type prior to mounting on the base units
OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH