A cesium surface $($work function $2\mathrm{.}1$ eV$)$ is illuminated with monochromatic light

of wavelength $400\mathrm{.}0$ nm$.$

a$.(1$ pt$)$ What is the maximum kinetic energy of the emitted photoelectrons?

b$.(1$ pt$)$ What is the cutoff wavelength for photoemission from a cesium electrode?