in {TAIL ~ step} {HEAD ~ each} of the second cooktop units is preassembled with 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
in { TAIL ~ step } { HEAD ~ each } of the second cooktop units is preassembled with 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
REL TAIL TAIL TAIL TAIL TAIL HEAD HEAD HEAD HEAD HEAD 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH