When photons each with energy 4.25 eV strike the surface of a metal A, the photoelectrons given out have maximum kinetic energy $$T_A$$ and the corresponding de Broglie wave length is $$\lambda_A$$. When another metal surface B is irradiated with photons each with energy 4.70 eV, the corresponding maximum kinetic energy $$T_B$$ is 1.50 eV less than $$T_A$$. If the de Broglie wave length $$\lambda_B$$ of these photoelectrons is twice that of $$\lambda_A$$, then