In this task, you need to count the number of times the given letter appears in the given sentence.
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Question: Sentence: 'a silver train crossing the road on tracks'. Find frequency of the letter 'r'

Answer: 5


Question: Sentence: 'some sheep are standing in a grassy field'. Find frequency of the letter 'n'

Answer: 3


Question: Sentence: 'a boy holding up a bat on a street at night'. Find frequency of the letter 'a'

Answer:
5