Can anyone help me solves these problems, I had try these problems but I still can not figure it out

Problem 1:  A certain brand of a parabolic satellite dish antenna has a diameter of six feet and a depth of one foot. How far from the vertex of the dish should the receiver be placed?

Problem 2:  The archway supporting a bridge over a 20-foot stream is in the shape of the top half of an ellipse. The highest point of the archway is five feet above the stream. How high is a point on the archway that is five feet (horizontally) from the end of the base of the archway?

Please anyone help me!!! Thanks so much