How would you be able to get these values?

For a step polymerization of monomers, ARA (with M0,A=90g/mole ) and BRB (with M0,B =140g/ mole), where R and R are hydrocarbon groups and AB can form a chemical bond. If the initial molar ratio of [ARA]/[BRB]=1.05 and 97% of BRB has reacted at the end of polymerization. Please estimate (A) the number average molecular weight of the polymer (10%) (B) the polydispersity of the synthesized polymer (7%)