A company has made an implant from a mixture of two linear

polymers, MDPE and HDPE, which are combined to create

one polymer. Assume all polymers are monodisperse and that

the molecular weight of MDPE is $100,000\frac{g}{m}ol$ and that of

the HDPE is $150,000\frac{g}{m}ol\mathrm{.}0\mathrm{.}1150\frac{g}{c}{m}^3$

The mixture is two parts by weight MDPE and four parts by

weight HDPE. Determine the number average molecular

weight.