What is the probability that picked character is one of the following letters I or N or D or A?

Question

An alphanumeric character is randomly picked from below quote by Lala Lajpat Rai
" The shots that hit me are the last nails to the coffin of the British rule in India "
What is the probability that picked character is one of the following letters I or N or D or A?
Note: Alphanumeric character means alphabet or number. Space or other characters should be ignored.

Answer 1

17/67

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There are total of 67 characters
Number of each A=5, D=1, N=4, I=7 - in total 17
So the probability would be 17/67