Given the two functions $f$ and $g$, find $fg$ and identify the domain.
$f\(\left\)(x\(\right\))=71x-2$, $g\(\left\)(x\(\right\))=x+10$

$fg\(\left\)(x\(\right\))=71x^2+712x-20$; Domain: $\(\left\)(-\(\infty\),\(\infty\)\(\right\))$

$fg\(\left\)(x\(\right\))=71x^2-712x-20$; Domain: $\(\left\)(-\(\infty\),0\(\right\))$

$fg\(\left\)(x\(\right\))=71x^2+708x-20$; Domain: $\(\left\)(-\(\infty\),\(\infty\)\(\right\))$

$fg\(\left\)(x\(\right\))=71x^2-708x-20$; Domain: $\(\left\)(-\(\infty\),\(\infty\)\(\right\))$