2-(5-(tert-Butyl)-2-hydroxy-4-(4-oxo-1,4-dihydroquinoline-3-carboxamido)phenyl)-2-methylpropanoic acid,4-[[(1,4-Dihydro-4-oxo-3-quinolinyl)carbonyl]amino]-5-(1,1-dimethylethyl)-2-hydroxy-alpha,alpha-dimethylbenzeneacetic Acid,Metabolite of Ivacaftor.,Ivacaftor Impurity