13. Flow time of 0.1 g.dL of poly(acryl amide) solution and pure water was measured as 216 s and 221 s at 30 C, respectively. The constants K and a are 68x105 and 0.66 for the polymer- solvent system, respectively. Assuming that the density of the polymer solution is equal to the density of water at this temperature, calculate the viscometric average molecular weight of the poly(acryl amide) sample. [M, = 6714 g/mol]