Need help with a task C#

[AdSaint]

A circle of radius r with center at point p with coordinates x is given
and y. Given a line y = b, parallel to the X axis. Determine whether the circle and the line intersect. If there is an intersection, then determine the coordinates of the intersection points.
Please help.

[dev7060]

A circle of radius r with center at point p with coordinates x is given
and y. Given a line y = b, parallel to the X axis. Determine whether the circle and the line intersect. If there is an intersection, then determine the coordinates of the intersection points.

What have you done so far?

[Luuk]

Google for "intersecti on of line and circle formula c#"