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

[Q]: Sentence: 'a large group of motorcycles parked along a street'. Find frequency of the letter 'a'
[A]: 5


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


[Q]: Sentence: 'a skateboarder zips along the bench at the park'. Find frequency of the letter 'a'
[A]:
6