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

[EX Q]: Sentence: 'a couple of men standing inside of a liquor store'. Find frequency of the letter 'p'
[EX A]: 1

[EX Q]: Sentence: 'a young woman dressed in green and black operating a remote control'. Find frequency of the letter 'r'
[EX A]: 5

[EX Q]: Sentence: 'picture of a pitcher throwing a ball and a baseball game'. Find frequency of the letter 'b'
[EX A]:
3