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

[Q]: Sentence: 'a doorway looking into a small bathroom with white toilet'. Find frequency of the letter 'r'
[A]: 2


[Q]: Sentence: 'the meal is served and ready to be eaten'. Find frequency of the letter 'e'
[A]: 8


[Q]: Sentence: 'a female tennis player holding a tennis racket'. Find frequency of the letter 'l'
[A]:
3