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

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

[EX Q]: Sentence: 'a piece of film shows two street signs crossing each other'. Find frequency of the letter 'f'
[EX A]: 2

[EX Q]: Sentence: 'baseball player in blue uniform throwing a pitch'. Find frequency of the letter 'w'
[EX A]:
1