Answer
$3944835.06 \ J$
Work Step by Step
We need to use the formula such as: $W=\int_a^b \rho g A(y) D(y) \ dy$.
Plug in the above formula the given values to obtain:
$W=\int_a^b \rho g A(y) D(y) \ dy\\=4 \pi \int_0^{4} \rho g (10-y) \ dy\\=4 \pi \times \rho g \times [10y-\dfrac{y^2}{2}]_0^4 \\=128 \rho g \pi\\=(128) (1000) (9.81) (\pi)\\=3944835.06 \ J$