These are the two known equations:
$$\frac{(I_2+I_3)-(I_1+I_4)}{I_1+I_2+I_3+I_4} = \frac{2x}{L}$$ $$\frac{(I_2+I_4)-(I_1+I_3)}{I_1+I_2+I_3+I_4} = \frac{2y}{L}$$
where I know the values of $(x,y,L)$. How can I find the values of $(I_1,I_2,I_3,I_4)$?