In this task, you need to count the number of times the given letter appears in the given sentence.
--------
Question: Sentence: 'three men in military suits are sitting on a bench,'. Find frequency of the letter 'a'

Answer: 3


Question: Sentence: 'a big bear walks through some grass'. Find frequency of the letter 'a'

Answer: 4


Question: Sentence: 'beautiful cathedral with tall spire reaching to the sky'. Find frequency of the letter 'u'

Answer:
2