Use the following information to answer the next two questions. Robert Millikan showed experimentally that Einstein's photoelectric equation Elmax = hf - W was valid. Using a variety of cathode materials, he measured the maximum kinetic energy of photoelectrons while varying the light frequency. The graph shown is typical for a particular cathode. The dotted line is an extrapolation (extension) of the experimental data. Maximum Kinetic Energy Un Frequency (Ha) The letters w, x, y, and z represent experimental or extrapolated data. 5) The value for Planck's constant could be determined with the expression A. W z -y W B. C. w(Z-y)_ 2 D. 6) The work function of the cathode material is equal to the expression W-x A. Z B. C. -x D. y