$3.$ A storm drain needs to be placed on a $1000-$ft long vertical curve which will be joining a $-4\mathrm{.}3\%$ grade line with a $+2\mathrm{.}8\%$ grade line. The vertex or intersection of the grade lines $($PVI$)$ is at station $35+00$ and the elevation there is at $135\mathrm{.}64.$ Determine the following:

Indicate if this is a sag or a crest curve.

The equation which defines the curve.

The stations for PVC and PVT$.$

The elevations of PVC and PVT$.$

The elevation at station $35+68.$

The station & elevation of the low point of the curve.

If the top of the drain is to be $4$ inches below the low point of the curve to prevent water accumulation and allow proper drainage, what would be the top elevation of the grate?