The values of the integrals $$\int_{0}^{1}\left ( \int_{0}^{1}\frac{x-y}{(x+y)^3}dy \right )dx$$ and $$\int_{0}^{1}\left ( \int_{0}^{1}\frac{x-y}{(x+y)^3}dx \right )dy$$ are

- same and equal to $0.5$
- same and equal to $-0.5$
- $0.5$ and $-0.5$, respectively
- $-0.5$ and $0.5$, respectively