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: 'two zebra stand near the wooden posts on a building'. Find frequency of the letter 't'
[EX A]: 4

[EX Q]: Sentence: 'a couple of birds are standing on the rocks'. Find frequency of the letter 'r'
[EX A]:
3