%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \sect{Average length of chain molecule} Molecule can be described as an ${N}$ monomers chain. The probability that a monomer will be horizontal is ${p}$ and then it's length is ${a}$, otherwise it's length is ${b}$. Let ${L}$ be the molecule's length. Find ${f\left(n\right)\equiv {p}\left(L=na+\left(N-n\right)b\right)}$. calculate ${\langle L\rangle}$ and ${\sigma_{L}}$, in two ways.\\ What is the behavior of ${\sigma_{L}/\langle L\rangle}$ as a function of ${N}$? %%begin{figure} \putgraph{Ex002} %%\caption{}\label{} %%end{figure}