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

[EX Q]: Sentence: 'a grey hummingbird by fence and tree branches'. Find frequency of the letter 'y'
[EX A]: 2

[EX Q]: Sentence: 'a man holding a frisbee high into the air'. Find frequency of the letter 'a'
[EX A]: 4

[EX Q]: Sentence: 'two guys in suits are walking down the street near others'. Find frequency of the letter 's'
[EX A]:
5