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

[Q]: Sentence: 'a group of tennis players on a tennis court'. Find frequency of the letter 'o'
[A]: 4


[Q]: Sentence: 'a man holding a frisbee high into the air'. Find frequency of the letter 'a'
[A]: 4


[Q]: Sentence: 'a collection of fruits are stacked on a plate'. Find frequency of the letter 'l'
[A]:
3