Answer
$374.85 \ J$
Work Step by Step
We calculate the work done to lift the 3-m chain by integrating as follows:
$ Work \ done =\int_{0}^{3} (9.8) (k(x)) \ x \ dx \\=9.8 \int_0^3 (x^3-3x^2+10 x) \ dx \\=9.8 \times [\dfrac{x^4}{4}-x^3+5x^2]_{0}^{3}\\=9.8 \times [\dfrac{(3)^4}{4}-(3)^3+5(3)^2] \\=374.85 \ J$
