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 
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
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