Which means that an equal number of groups B will be consumed when group A is reacted completely. The number of the mixture before the reaction is 𝑁 𝑎 + 𝑁 𝑏 . The corresponding number of polymer mixtures will be reduced when one group of A reacts. Then the number of molecules consumed will be 𝑓 𝑎 ̅ • 𝑁 𝑎 because the total number of group A is 𝑓 𝑎 ̅ • 𝑁 𝑎 . So, the final number of the polymer mixture is: