Photons with a frequency of 1.0 × 1020 hertz strike a metal surface. If electrons with a maximum kinetic energy of 3.0 x 10-14 joule are emitted, the work function of the metal is

1. 1.0 x 10-14 J
2. 2.2 x 10-14 J
3. 3.6 x 10-14 J
4. 6.6 x 10-14 J