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

[EX Q]: Sentence: 'two zebras feed on a plant through some wire mesh'. Find frequency of the letter 'o'
[EX A]: 4

[EX Q]: Sentence: 'a sheep in a field in front of other sheep'. Find frequency of the letter 'f'
[EX A]: 3

[EX Q]: Sentence: 'a yellow two way traffic sign sitting on the side of a road'. Find frequency of the letter 'a'
[EX A]:
5