I cant get the answers to these four problems

Please if you cant answer all of them ,,, atleast answer the one which you can,,,

Thanks a lot in advance ,, i’d be really greatful to you ….

1) The photoelectric current from a photo cell can be reduced to zero by a stopping potential of 2.5V when a monochromatic light is incident on cathode. If work function of cathode is 3.7eV find the wave length of the light.

2) The work function of the metal is 2.2eV. Find Maximum velocity of electrons when light of wavelength of 3*[10^(-7)] metres is incident

m=9.1 * 10^(-31) kg

3)

Light of wavelength 5000AU falls on photoemitter. The stopping potential of photo electrons emitted its 0.45v.

Find the maximum energy of emitted photoelectrons.

4) A light of wavelength 2000Au falls on metal surface for which the photoelectric work fucntion is 4.2ev. Find the KE of the slowest and fastest electrons emitted. What is stopping potential and threshold wavelength ?