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

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


[Q]: Sentence: 'a closet with a fan, luggage and various boxes'. Find frequency of the letter 'a'
[A]: 6


[Q]: Sentence: 'a double decker bus parked in a field next to a bunch of trees'. Find frequency of the letter 'r'
[A]:
3