In this task, you need to count the number of times the given letter appears in the given sentence.

[EX Q]: Sentence: 'this is a sign in front of a large cathedral'. Find frequency of the letter 'a'
[EX A]: 5

[EX Q]: Sentence: 'a passenger bus that is driving down the street'. Find frequency of the letter 'r'
[EX A]: 3

[EX Q]: Sentence: 'two people in a snowy place near a wooden fence'. Find frequency of the letter 'n'
[EX A]:
5