Parabola: co-ordinates of the focus & tangent

Hey, I'm struggling with this question:

The point P $\displaystyle (at^2, 2at)$ lies on the parabola C with equation$\displaystyle y^2=4ax$ where a is a positive constant. The point Q lies on the directrix of C. The point Q also lies on the X axis.

State the co-ordinates of the focus of C and the co-ordinates of Q.

The tangent to C at P passes through the point Q.

Also, find, in terms of a, the two sets of possible coordinates of P.

I don't know where to get stared with this question.