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

[Q]: Sentence: 'small airplane in the process of taking off'. Find frequency of the letter 'e'
[A]: 3


[Q]: Sentence: 'a man using a video game controller in a room'. Find frequency of the letter 'n'
[A]: 4


[Q]: Sentence: 'a city view of the streets and harbor on a  sunny day'. Find frequency of the letter 'f'
[A]:
1