The intersection of two planes is (x+y+z−6)+λ(2x+3y+4z+5)=0 ⇒(1+2λ)x+(1+3λ)y+(1+4λ)z+(−6+5λ)=0 ...(i) Since, this plane is perpendicular to the plane 4x+by−3z−8=0 . ∴(1+2λ)4+(1+3λ)5+(1+4λ)(−3)=0 On putting the value of λ in Eq. (i), we get (−