I am trying to figure out the "equation" or other means of finding the exact shape in the figure below. It's somewhat of a pyramid with a rectangular base, but the sides are curved rather than flat. I have found how to make the longer sides (simple half-circle) but the narrow two sides I can't quite figure out. The long edge is 40" and the shorter edge is 30".

Can anyone tell me exactly how to calculate the measurements/curves of the narrower side (third picture)?

NOTE: The narrow side in the third picture is really just a trial-and-error cut-out, no measurements or calculations were done to determine what it should look like.

Thanks!

Can you provide the length (longest side) & width (shorter side) and with a tape measure, give the length along the curved part from the bottom corner to BELOW the rectangle thing on top (just need one assuming all four curved parts are equal). For the rectangle thing on top, just multiply the length x width x height to get the volume for that.

How tall is this from bottom to top and the length of the bottom edge?