10. The cost of a house consists of the cost of the above-ground part and the cost of the foundation part. For a house with an area of $N \mathrm{~m}^{2}$, the cost of the above-ground part is proportional to $N \sqrt{N}$, and the cost of the foundation part is proportional to $\sqrt{N}$. It is known that for a house with an area of $3600 \mathrm{~m}^{2}$, the cost of the above-ground part is $72 \%$ of the cost of the foundation part. Therefore, to build several identical houses with a total area of $80000 \mathrm{~m}^{2}$ at the minimum total cost, the area of each house in square meters should be $\qquad$