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

• A. $fg\left(x\right)=71x^2+712x-20$; Domain: $\left(-\infty,\infty\right)$
• B. $fg\left(x\right)=71x^2-712x-20$; Domain: $\left(-\infty,0\right)$
• C. $fg\left(x\right)=71x^2+708x-20$; Domain: $\left(-\infty,\infty\right)$
• D. $fg\left(x\right)=71x^2-708x-20$; Domain: $\left(-\infty,\infty\right)$