Third Bohe orbit corresponds to principle quantum number, n = 3.

Now, energy of an electron in n = n is En= - 13.6/ n^2 eV for hydrogen atom.

Now, in Bohr's theory we come across the result:En= (1/2) ( potential energy).

Therefore, (1/2)(potential energy )=-(13.6/9)eV.

Therefore, potential energy =-27.2/9 eV……………..(1)

Now, kinetic energy K = total energy - potential energy

Then, K=-13.6/9-(-27.2/9)=13.6/9 eV.