Let a, r, s, t be non-zero real numbers. Let `P(at^(2),2at),Q(ar^(2),2ar)andS(as^(2),2as)` be distinct points on the parabola `y^(2)=4ax`. Suppose that PQ is the focal chord and lines QR and PK are parallel, where K the point (2a,0).
If st=1, then the tangent at P and the normal at S to the parabola meet at a point whose ordinate is

Options

A. `((t^2+1)^2)/(2t^3)`
B. `(a(t^2+1)^2)/(2t^3)`
C. `(a(t^2+1)^2)/(t^3)`
D. `(a(t^2+2)^2)/(t^3)`

Answer

B