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

[EX Q]: Sentence: 'several zebras  and a giraffe in an enclosure'. Find frequency of the letter 's'
[EX A]: 3

[EX Q]: Sentence: 'some sheep are standing in a grassy field'. Find frequency of the letter 'n'
[EX A]: 3

[EX Q]: Sentence: 'small black bird with red on its head standing on a tree branch'. Find frequency of the letter 'b'
[EX A]:
3