One kilogram of a polyester with a number-average molar mass M – n = 10,000 g mol−1 is mixed with one kilogram of another polyester with a M – n = 30,000 g mol−1. The mixture then is heated to a temperature at which ester interchange occurs and the heating continued until full equilibration is achieved. Assuming that the two original polyester samples and the new polyester, produced by the ester interchange reaction, have the most probable distribution of molar mass, calculate M – n and weight-average molar mass M – w for the mixture before and after the ester interchange reaction.