Let $g^{\prime }\left(x\right)$ be continuous for all real $x$. What is the average value of $g^{\prime }\left(x\right)$ on the interval $[2,7]$?

$\frac{g\left(2\right)+g\left(7\right)}{2}$

$\frac{g^{\prime }\left(2\right)+g^{\prime }\left(7\right)}{2}$

$\frac{g\left(7\right)-g\left(2\right)}{5}$

$\frac{g^{\prime }\left(7\right)-g^{\prime }\left(2\right)}{5}$