In the image of the cartography, a contour line will join points of equal elevations thus the contour interval in a contour map shows the difference in elevation between successive contour lines. Topographic maps use contours to represent the terrain of a region. The darker contour lines on the map are index contour lines.
According to the image, the contour lines passes through 25, and B located between 75 and 100 feet thus the nearest option will be 80 feet Point X is located above 125 feet in the elevation thus the best pick will be 135 feet.
