Blue light with a wavelength of 420 nm is incident on a certain material and causes the

Question:

Blue light with a wavelength of 420 nm is incident on a certain material and causes the emission of photoelectrons with a maximum kinetic energy of 1.00 x 10-19 J.
(a) What is the stopping voltage?
(b) What is the material’s work function?
(c) What is the stopping voltage if red light (λ = 700 nm) is used instead? Explain.