For what values of x does f x 5x 10 sin x have a horizontal tangent line Choose the correct answer below TU 5 O A x 2k and x 2k where k is any integer 3 3 T 5ft B x 2kx and x 2kx where k is any integer 6 T 5T O c x k and x k where k is any integer 3 3 R6 OD x k and x 5T 6 k where k is any integer