11.1 - Using contour maps

Consider the following contour map of a continuous function $f(x,y)$.

1. For approximately what values of $y$ is it true that $10 \leq f(5,y) \leq 30$?
2. What do you estimate $f(2,4)$ to be, and why?
3. What do you estimate for $f(6,6)$? Explain.
4. How many values of $y$ satisfy $f(7,y)=20$? (Hint: Draw a line that includes all the points having coordinates $(7,y)$ where $y$ could be any real number.)
5. How many values of $x$ satisfy $f(x,8)=20$?