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

[Q]: Sentence: 'a man holding a baseball bat an playing baseball'. Find frequency of the letter 'l'
[A]: 6


[Q]: Sentence: 'a person on a surfboard in the surf of a wave'. Find frequency of the letter 's'
[A]: 3


[Q]: Sentence: 'a little boy chewing on a tooth brush that is still in the wrapper'. Find frequency of the letter 'l'
[A]:
4