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

[Q]: Sentence: 'there is a sandwich with a lot of meat cut in half'. Find frequency of the letter 'a'
[A]: 5


[Q]: Sentence: 'a person that is looking out his window'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'two men are talking around a counter at a store'. Find frequency of the letter 'r'
[A]:
4