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

[Q]: Sentence: 'a person is riding in a cart pulled by a horse'. Find frequency of the letter 'a'
[A]: 4


[Q]: Sentence: 'a young elephant is touching a bigger elephant with its trunk'. Find frequency of the letter 'i'
[A]: 5


[Q]: Sentence: 'different sets of luggage in a baggage claim area'. Find frequency of the letter 'r'
[A]:
2