1. No. beginning with a given vowel     = 21 * 5 = 105
     No. beginning with a given consonant = 5 * 21 = 105
       So total = 5 * 105 + 21 * 105 = 2730

  2. First word in Vol.II = Word no. 2730/3 + 1 = 911
     Now ABA is Word no.1
     So  BAB is Word no.106
          .... (counting in steps of 105)
     So  IBA is Word no.841
     So  ICA is Word no.846
          .... (counting in steps of 5)
     So  ISA is Word no.911
 
  3. Solved similarly, with one additional step to find
      third letter.