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

[Q]: Sentence: 'a tennis player after hitting a shot back to the other side of the court'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'old double decker bus parked in a lot'. Find frequency of the letter 't'
[A]: 1


[Q]: Sentence: 'a man and a woman sitting on a park bench'. Find frequency of the letter 'a'
[A]:
7