3. There is a polymer prepared by step polymerization using difunctional monomers, RA2 and RB2. (a) Assuming 1:1 stoichiometry of mutually-reactive functional groups, calculate the number-average molar mass of the polymer when 96% of initial number of functional groups have reacted. 7,500 g/mol (b) When RB2 is in excess with a molar ratio of 1:1.2 (RA2:RB2), calculate the number-average molar mass of the polymer. Assume that 80% of initial number of B functional groups remained unreacted. 384 g/mol (c) When the RB2 is replaced by trifunctional monomers RB3, calculate the extent of reaction and number-average degree of polymerization. Assume that the 8% of initial number of RA2 molecules remained unreacted and the molar ratio of RA2 and RB3 is 4:1. p = 0.84, x = 13.15 Assumptions: (1) Neglect contributions from end groups; (2) the molar masses of RA2 and RB2 are 240 and 360 g/mol, respectively; (3) The molar mass of RB3 is 390 g/mol.