In the International system of notation for numbers letters ‘a’, ‘b’, ‘c’, and ‘d’ do not appear anywhere in the spelling of 1 to 99.
Letter, ‘d’ comes for the first time in hundred.
Letters ‘a’ ‘b’ and ‘c’ do not appear anywhere in the spellings of 1 to 999.
‘a’ comes for the first time in thousand.
Letters ‘b’ and ‘c’ do not appear anywhere in the spellings of 1 to 999,999,999.
Letter ‘b’ comes for the first time in billion.
Letter ‘c’ does not appear in the spelling of any number.