Answer
Please see the figure attached.
Work Step by Step
The contour map of $f\left( {x,y} \right) = x + y$ with contour interval $m=1$ is obtained by plotting the lines:
$c = x + y$, ${\ \ \ }$ for $c = ..., - 4, - 3, - 2, - 1,0,1,2,3,4,...$
Similarly for the contour interval $m=2$, the contour map is obtained by plotting the lines:
$c = x + y$, ${\ \ \ }$ for $c = ... - 4, - 2,0,2,4,...$
