ACR ON VISUAL APCH TO DEN EXPERIENCED TCASII RA WITH ATC ISSUED TFC.

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WE WERE ON APCH TO RWY 35R AT DEN. APCH CTL CLRED US TO 7500 FT AND THEN CLRED US FOR A VISUAL APCH. FO DSNDED TO 7000 FT WHICH IS ALT FOR FAF (FRONZ). ATC CALLED TFC WHICH WE DID NOT SEE AND THEN TOLD US TO TURN L TO 270 DEG HDG TO AVOID TFC. IN THE TURN WE GOT AN RA TO 'CLB' AND FO STARTED AN IMMEDIATE CLB. I THEN SAW A LIGHT ACFT BELOW AND STRAIGHT AHEAD. IT'S POSSIBLE THAT WE WERE BELOW THE TCA FLOOR OR THE LIGHT ACFT WAS IN THE CLASS B AIRSPACE. LOOKING AT THE COMMERCIAL CHART PAGE LATER ON; I BELIEVE WE WERE IN AN AREA WITH A 7000 FT FLOOR (MAYBE EVEN 6500 FT). ADDING TO THE CONFUSION WAS THE FACT THAT DEN CHANGED OUR RWY 2 TIMES -- RWY 26 TO RWY 35L TO RWY 35R. SO WE HAD A VERY HIGH WORKLOAD. ALTHOUGH ATC CAN BE EXTREMELY BUSY; THEY ARE INTIMATELY FAMILIAR WITH THEIR OWN AIRSPACE; AND I WOULD THINK WE COULD BE WARNED IF WE GOT TOO LOW. (COULD THE CTLR'S SCREEN GIVE HIM A WARNING IF WE WERE TOO LOW?) WE MIGHT ONLY FLY INTO ANY GIVEN ARPT A FEW TIMES A YR; YET WE ARE EXPECTED TO DYNAMICALLY INTERP THE INFO FROM THAT SMALL COMMERCIAL CHART PAGE. (IMPOSSIBLE IF YOU GET 2 RWY CHANGES!)