Answer
$$
5.66 \times 10^{9} \mathrm{N} .
$$
Work Step by Step
The total weight is
$$
W=\rho g V=\rho g h A$$$$=\left(1030 \mathrm{kg} / \mathrm{m}^{3}\right)\left(9.8 \mathrm{m} / \mathrm{s}^{2}\right)(255 \mathrm{m})\left(2200 \mathrm{m}^{2}\right)=5.66 \times 10^{9} \mathrm{N} .
$$
