i.4.47 Curvilinear integrals

condition: Calculate the curve integral \( \int_{L} f(x, y) d x+g(x, y) d y \) \( f(x, y)=x^{2}-y, \quad g(x, y)=y^{2}-x \), \( L: \) rectangle \( x=0, y=0, x=1, y=2\).