I assume you want the Mulliken electronegativity, since you provided ionization energy and electron affinity in eV.
ΧM = Mulliken electronegativity
Ei = ionization energy = 13.0 eV
Eea = electron affinity = 3.8 eV
XM = 0.187(Ei + Eea) + 0.17, with Ei and Eea in eV
ΧM = 0.187(13.0 + 3.8) + 0.17 = 3.31
This is different from the given options, but the closest one is 3.5