How many milliliters of .085 m naoh are required to titrate 25 ml of .072 m hbr to the equivalence point?

The ML  of 0.85  m NaOH    required   to  titrate  25 ml of  0.72m hbr  to  the  equivalence  point  is calculated  as  follows

calculate  the moles  of HBr used

moles  = molarity  x  volume

25  x0.072/1000=  0.0018 moles

write the  equation  for  reaction

NaOH + HBr = NaBr  +  H2O
from   reacting   equation the  mole ratio  between  NaOH  to  HBr  is  1:1  therefore  the  moles of  NaOH  =  0.0018 moles

volume   =  moles/molarity
0.0018/0.085 =  0.021  L  in Ml  =  0.021  x1000=21.18 Ml  ofNaOH

Ais the correct answer

And a) oxygen i believe