When responding to sound, the human eardrum vibrates about its equilibrium position. Suppose an eardrum is vibrating with an amplitude of $7\mathrm{.}8$ x$10-7$ m and a maximum speed of $2\mathrm{.}2$ x$10-3$ m$/$s$.($a$)$ What is the frequency $($in Hz$)$ of the eardrum's vibrations? $($b$)$ What is the maximum acceleration of the eardrum?