$${W = \int_2^3 3x^2\, dx + \int_3^0 4\, dy = 3 \int_2^3 x^2\, dx + 4 \int_3^0 dy \\ = 3 [\frac{1}{3} x^3]_2^3 + 4[y]_3^0 = [3^3 + 2^3] + 4 [0 - 3] \\ = \underline{\underline{7,0\, \mathrm{J}}}}$$