Slope of the topographic surface

Star Villa (1555) is surrounded by game reserve "Obora Hvězda".[br]Determine the highest slope of the circled area.
Slope is determined by contour lines. The closer countours means the steeper terrain. [br]The smallest distance of neigbouring contour lines is estimate by the circle with radius r.[br] slope = rise (5) over run (2r).

Information: Slope of the topographic surface