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

[Q]: Sentence: 'a young boy bouncing a tennis ball on a tennis racquet'. Find frequency of the letter 'a'
[A]: 5


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


[Q]: Sentence: 'this is a close up view of a tennis player during the game'. Find frequency of the letter 't'
[A]:
3