0.2-g sample of amylopectin was analyzed to determine the frac- tion of the total glucose residues that are branch points in the struc- ture. the sample was exhaustively methylated and then digested, yielding 50 mol of 2,3-dimethylglucose and 0.4 mol of 1,2,3,6- tetramethylglucose. a. what fraction of the total residues are branch points? b. how many reducing ends does this sample of amylopectin have?