Equimolar hexamethylenediamine and adipic acid are polymerised until $p=0.995$ of the functional groups have reacted. Use ${\overline{X}}_n=1/(1-p)$ for the number-average number of monomer molecules per chain, and take the repeat unit of nylon 6,6 (one diamine residue plus one diacid residue) as 226 g/mol; neglect end groups. The number-average molar mass is

1. A$22600\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$
2. B$45200\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$
3. C$11300\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$
4. D$226\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$