Why does the author include a description of Rube Goldberg's invention, "The Self-Operating Napkin"?

Read the excerpt from poe’s "the fall of the house of usher." his ordinary occupations were neglected or forgotten. he roamed from chamber to chamber with hurried, unequal, an objectless step. the pallor of his countenance had assumed, if possible, a more ghastly hue -- but the luminousness of his eye had utterly gone out. which statement best describes the effect of the narration on the story? the narration reveals usher’s feelings of discouragement. the narration reveals usher’s absent-mindedness after his loss. the narration suggests usher’s confusion in the wake of his loss. the narration suggests usher’s mental decline after his sister’s death.