Vertical Curves grade on crest curve

I am working this problem which asked for the grade (in %) on the declining tangent piece of a crest vertical curve, but having a hard time completing it in a timely manner. The problem gives the PVC station and elevation, PI station and elevation, elevation and station at the End of Vertical curve and the length of the curve, What's the formula, or quickest way to solve this problem given these variables. I use the formula (in School of PE notes), which is used to find curve elevation at a given point on the curve, but in this case I have the curve elevation, but not enough information to used it with (R=(g2-g1)/2) since the g2 is unknown. Any help is appreciated. :beat:

^^^ What he said.

Thank you Major Highway.

The "tricky" part in this question is to know that the stationing is measured along the horizontal projection from the PVC to the PVT (i.e. the segment known as the length of the vertical curve) and not along the parabolic curve.