Two Surfaces, a and B, Are Illuminated by Light of the Same

Two surfaces, A and B, are illuminated by light of the same wavelength. Both surfaces emit photoelectrons. If the stopping potentials are $\phi$ and 2 $\phi$ , respectively, their kinetic energies are related by

A) K_A - K_B = $\phi$
B) K_B - K_A = $\phi$
C) K_A + K_B = $\phi$
D) K_A + K_B = 3 $\phi$
E) None of the above is correct.