Let $g \in C_{b}(\mathbb{R})$ satisfying hypothesis A (i.e., $g$ is of class $C^{\infty}$ on $\mathbb{R}$, bounded, and all its derivative functions of all orders are bounded on $\mathbb{R}$).\\
Deduce the set of functions $g$ satisfying hypothesis A and such that $N_{g}$ has finite codimension in $L^{1}(\mathbb{R})$.