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

[EX Q]: Sentence: 'a couple of buildings that has a bus out front'. Find frequency of the letter 'a'
[EX A]: 4

[EX Q]: Sentence: 'a person is water skiing and there are birds flying around above them'. Find frequency of the letter 'n'
[EX A]: 5

[EX Q]: Sentence: 'two slices of pizza on a paper plate with a bite taken out of one'. Find frequency of the letter 'f'
[EX A]:
2