$${da_g = -2 \frac{(6,67 \times 10^{-11}\, \mathrm{m^3/kg \cdot s^2})(1,99 \times 10^{31}\, \mathrm{kg})}{(6,77 \times 10^6\, \mathrm{m})^3} (1,70\, \mathrm{m}) \\ = \underline{\underline{-14,5\, \mathrm{m/s^2}}}}$$