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

[EX Q]: Sentence: 'a flock of sheep grazing in a park'. Find frequency of the letter 'f'
[EX A]: 2

[EX Q]: Sentence: 'a man serving himself pizza in a wooden booth'. Find frequency of the letter 'n'
[EX A]: 4

[EX Q]: Sentence: 'a man standing on the beach next to a surfboard'. Find frequency of the letter 'n'
[EX A]:
5