Finding average value of function over given region The function is $f(x,y)=2x^3+y^2-6xy-20y-14$ and the vertices are $(-4,2), (-4,8), (8,2)$.
I got $301.56$ but I dont know if I set my integrations right. I made the first integral $8$ to $2$ and the secone $8$ to $-4$ and found the are was $36$.

HINT:
$$\int_{-4}^{\ 8}\int_{2}^{-\frac{1}{2}x+6}f(x,y)dydx$$
The rest is only "hard work"
