The function $f(x)$ changes value when $x$ changes from $x_0$ to $x_0+dx.$ Find the approximation error $|f-df|.$ Round your answer to three decimal places.

$f(x)=\frac{1}{x^2},x_0=2,dx=0\mathrm{.}8$

A$.0\mathrm{.}329$

B$.0\mathrm{.}022$

C$.0\mathrm{.}078$

D$.0\mathrm{.}405$