Letters 'a', 'b', 'c ' & 'd' do not appear anywhere in the spellings of 1 to 99
Letter 'd' comes for the first time in Hundred
Letters 'a', 'b' & 'c ' do not appear anywhere in the spellings of 1 to 999
Letter 'a' comes for the first time in Thousand
Letters 'b' & 'c' do not appear anywhere in the spellings of 1 to 999,999,999
Letter 'b' comes for the first time in Billion
And
Letter 'c' does not appear anywhere in in the spellings of entire English Counting
Letter 'd' comes for the first time in Hundred
Letters 'a', 'b' & 'c ' do not appear anywhere in the spellings of 1 to 999
Letter 'a' comes for the first time in Thousand
Letters 'b' & 'c' do not appear anywhere in the spellings of 1 to 999,999,999
Letter 'b' comes for the first time in Billion
And
Letter 'c' does not appear anywhere in in the spellings of entire English Counting