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 passenger bus that is driving down the street'. Find frequency of the letter 'r'

Answer: 3


Question: Sentence: 'a man and several white red and blue airplanes'. Find frequency of the letter 'u'

Answer: 1


Question: Sentence: 'a red and yellow sign is attached to a pair of scissors is on a brown building'. Find frequency of the letter 'i'

Answer:
7