### Still have math questions?

Among all rectangular regions $$0 \leq x \leq a , 0 \leq y \leq b$$ , find the one for which the total outward flux of $$F = ( x ^ { 2 } + 4 x y ) i - 6 y j$$ across the four sides is least. What is the least flux?
$$a = 2 , b = 1 \text { . The minimum flux is } - 4$$