If all the vertices of an equilateral triangle lie on the parabola $y^2=16 x$ and one of them coincides with the vertex of that parabola, then the length of the side of that triangle is

If $m x-y+c=0$ is a normal at a point $P$ on the parabola $y^2=16 x$ and the focal distance of $P$ is 40 units, then $|c|=$

If a circle with its centre at the focus of the parabola $y^2=2 p x$ is such that it touches the directrix of the parabola, then a point of intersection of the circle and the parabola is

If the tangent drawn at the point $P(4,8)$ to the parabola $y^2=16 x$ meets the parabola $y^2=16 x+80$ at $A$ and $B$, then the mid-point of $A B$ is