How do you find the highest value on a contour map?

On most topographic maps, index contour lines are generally darker and are marked with their elevations. Lighter contour lines do not have elevations but can be determined by counting up or down from the nearest index contour line and multiplying by the contour interval. The contour interval is stated on every topographic map and is usually located below the scale.

reflecting point a across the origin negates both of its coordinates.

b = (5, -4)