Question

what is the difference in the two surface areas of the figures

Answer 1

This just requires a lot of calculations.

The areas of the bases are length x width.

Each figure has four triangular sides.
The areas of the sides are those of triangles, (1/2) base x height,
but getting the heights requires dropping a line from the apex
of each to the base, then finding the length of this height from
the Pythagorean formula of hypotenuse^2 = side1^2 + side2^2.