\lambda(A^c)={\int\int\int}_{A^c}\,\,dz\,dy\,dx=\int_0^1 \int_{\frac{1}{2x}}^1 \int_{\frac{1}{2xy}}^1 dz\,dy\,dx=
\int_0^1 \int_{\frac{1}{2x}}^1 (1-\frac{1}{2xy})\,dy\,dx=...