Originally Posted by

**earboth** I placed the origin of a coordinate system at the red dot.

Then you are looking for a parabola with the equation

$\displaystyle y = ax^2+c$

From your drawing you get:

$\displaystyle B(0,-2)$

$\displaystyle A(-50,-8)$

Plug in the coordinates of the points into the equation of the parabola:

$\displaystyle -2=c$

$\displaystyle -8=a(-50)^2-2~\implies~a=-\frac6{2500}$

Thus the equation of the parabola is:

$\displaystyle y=-\frac6{2500} x^2-2$

Use this equation to answer the other questions of your problem.