{HEAD ~ a pair} of liquid containers at substantially the same level including a water container and {TAIL ~ a detergent container} 
{ HEAD ~ a pair } of liquid containers at substantially the same level including a water container and { TAIL ~ a detergent container }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL