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 red and white train passing a train station'. Find frequency of the letter 'a'

Answer: 7


Question: Sentence: 'girls posing of a picture one holding a tennis racket the other wearing a crown'. Find frequency of the letter 'g'

Answer: 4


Question: Sentence: 'two mounted policemen sit atop their horses on a city street'. Find frequency of the letter 'o'

Answer:
6