A mirror has a parabolic surface defined by the equation y =¹⁄₂₄ x² with the vertex (0, 0) at the center of the mirror. When the width of the mirror is 8 inches, what is the depth, y, of the mirror?
A.) ¹⁄₃₆ in.
B.) ⅙ in.
C.) ⅔ in.
D.) 2⅔ in.