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