We present a measurement of the ratio of the top-quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q represents quarks of type b, s, or d, in the final state with a lepton and hadronic jets. The measurement uses root s = 1.96 TeV proton-antiproton collision data from 8.7 fb(-1) of integrated luminosity collected with the Collider Detector at Fermilab during Run II of the Tevatron. We simultaneously measure R = 0.94 +/- 0.09 (stat + syst) and the t (t) over bar production cross section sigma(t (t) over bar) = 7.5 +/- 1.0 (stat + syst) pb. The magnitude of the Cabibbo-Kobayashi-Maskawa matrix element, vertical bar V-tb vertical bar = 0.97 +/- 0.05 (stat + syst) is extracted assuming three generations of quarks, and a lower limit of vertical bar V-tb vertical bar > 0.89 at 95% credibility level is set.
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