Please bear with me because I have only little experience in using codes to construct the symbols for the equations. The question is:
Determine the average value of $f(x,y) = x^2 y^2$, in the region $$R: a\le x\le b, c\le y\le d,$$ where $a+b=5, ab=13, c+d=4, cd=7.$
The formula for average value is
Please use only elementary calculus, and no complex analysis. Much appreciated!