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

[Q]: Sentence: 'a dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'
[A]: 2

[Q]: Sentence: 'a red and white train passing a train station'. Find frequency of the letter 'a'
[A]: 7

[Q]: Sentence: 'heavy traffic going and coming on a busy highway'. Find frequency of the letter 'f'
[A]:
2