What's the surface area formula for wedges?

I assume you have

a rectangular base and sloping face
two triangular sides
a rectangular face at the back.

I'm sure you know how to find each kind of area, so just add them up.

As for the surface area, the main problem is the upper surface - it's a curved surface. This is a matter of advanced mathematics, and I have long forgotten it.

Therefore, I need the full formula, not the procedure