Calculate for a hydrogen atom and a He + ion: (a) The radius of the first Bohr

Question:

Calculate for a hydrogen atom and a He + ion:
(a) The radius of the first Bohr orbit and the velocity of an electron moving along it;
(b) The kinetic energy and the binding energy of an electron in the ground state;
(c) The ionization potential, the first excitation potential and the wavelength of the resonance line (n' = 2 →n = l).