$${f = \frac{2 \mu_z B}{h} = \frac{(2)(1,41 \times 10^{-26}\, \mathrm{J/T})(1,80\, \mathrm{T})}{6,63 \times 10^{-34}\, \mathrm{J \cdot s}} \\ = 7,66 \times 10^7\, \mathrm{Hz} = \underline{\underline{76,6\, \mathrm{MHz}}}}$$