Part a: The wavelength of the radiation is 1.5*10^-11 m, which corresponds to an energy of around 83 eV. This energy is much higher than the energy of visible light, which ranges from 1.8 to 3.1 eV. Therefore, these radiations would not be visible to the human eye.
Part b: The wavelength of the radiation is 3*10^7 m, which corresponds to an energy of around 4*10^-16 eV. This energy is much lower than the energy of visible light, which ranges from 1.8 to 3.1 eV. Therefore, these radiations would also not be visible to the human eye.
