in step each of {HEAD ~ the second cooktop units} is preassembled with {TAIL ~ a respective single cooking system type} prior to mounting on the base units, and at least one of the second cooktop units has a cooking system type different than that of the other two second cooktop units 
in step each of { HEAD ~ the second cooktop units } is preassembled with { TAIL ~ a respective single cooking system type } prior to mounting on the base units , and at least one of the second cooktop units has a cooking system type different than that of the other two second cooktop units
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH