$${F = 300\, \mathrm{N} + \frac{(0,12\, \mathrm{m})(80\, \mathrm{kg})(9,8\, \mathrm{m/s^2})}{0,30\, \mathrm{m}} \\ = 613,4\, \mathrm{N} \approx \underline{\underline{610\, \mathrm{N}}}}$$