Oxygen has 5 degree of freedom `:.` Energy per mole of oxygen = `5/2 RT`
For 2 moles of oxygen , energy, `E_(1) = 5RT`
Neon has 3 degrees of freedon `:.` Energy per mole of neon = `3/2 RT`
For 4 moles of neon energy , `E_(2) = 4 xx 3/2 RT = 6RT`
Total energy of mixture = `E_(1)+E_(2)= 5RT + 6RT= 11 RT`.