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

[Q]: Sentence: 'a player swings his bat at a baseball game'. Find frequency of the letter 'p'
[A]: 1


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


[Q]: Sentence: 'a bathroom with two mirrors, sink and shower stall'. Find frequency of the letter 'o'
[A]:
5