For equation $x(t)=x_{m}cos({}_{d}t+)$ suppose the amplitude $x_m$ is given by

$x_m=\frac{F}{[m^2({}_d^2-{}^2{)}^2+b^2{}_d^2{]}^{\frac{1}{2}}}$

where $F$ is the $($constant$)$ amplitude of the external oscillating force exerted on the spring by the rigid support in the figure.

NOTE: Give your answer in terms of the variables given.

$($a$)$ What is the amplitude of the oscillating object at resonance?

$x_m=$

$($b$)$ What is the velocity amplitude of the oscillating object at resonance?

$v_m=$