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

[EX Q]: Sentence: 'two men sitting quietly on a park bench'. Find frequency of the letter 'a'
[EX A]: 2

[EX Q]: Sentence: 'a bathroom that has it's lights turned on'. Find frequency of the letter 'h'
[EX A]: 4

[EX Q]: Sentence: 'a southwest commercial airplane flying in the sky'. Find frequency of the letter 'e'
[EX A]:
4