Question: Let $f$ and $\mathrm{g}$ be differentiable functions on $\mathbf{R}$ such that fog is the identity function. If for some $a, b \in \mathbf{R}, g^{\prime}(a)=5$ and $g(a)=b$, then $f^{\prime}(b)$ is equal to :
$\frac{2}{5}$
1
$\frac{1}{5}$
5
Correct Option: , 3
Solution:
