Please tell me how to do this problem.

Advantages:

The four supporting legs are connected and fixed by tenon-mortise structure, which is more firm;

Disadvantages:

The area enclosed by the upright support legs is small, so people sit off-center, and their center of gravity is easy to move out of the support surface and fall down.

Bandeng B.

Advantages:

All the supporting legs diverge outward, and the supporting surface becomes larger and more stable;

Disadvantages:

There is no structural connection between the support legs, especially when the outwardly flaring support legs have vertical downward force, it is easy to form a large bending moment between the stool legs and the stool surface, which makes the mortise and tenon of the joint surface loose or even broken.