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

[EX Q]: Sentence: 'a black bear sitting in the grass taking a rest'. Find frequency of the letter 'a'
[EX A]: 6

[EX Q]: Sentence: 'a young boy standing in front of a counter with dougnuts'. Find frequency of the letter 'o'
[EX A]: 6

[EX Q]: Sentence: 'a couple is on the court playing tennis'. Find frequency of the letter 'o'
[EX A]:
3