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: 'two metal benches on an empty train platform'. Find frequency of the letter 'n'

Answer: 4

Question: Sentence: 'a red fire hydrant opened and spilling water'. Find frequency of the letter 'd'

Answer: 4

Question: Sentence: 'a tennis player finishing a swing in front of an audience'. Find frequency of the letter 'f'

Answer:
3