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

[EX Q]: Sentence: 'a man in a black shirt prepares to catch a frisbee'. Find frequency of the letter 'f'
[EX A]: 1

[EX Q]: Sentence: 'a woman and a child walking down a street with a kite'. Find frequency of the letter 'n'
[EX A]: 4

[EX Q]: Sentence: 'a person is cutting blue plastic with a pair of scissors'. Find frequency of the letter 's'
[EX A]:
7