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

[Q]: Sentence: 'a jet that is flying in the sky with a banner behind it'. Find frequency of the letter 'r'
[A]: 1


[Q]: Sentence: 'a boy swinging a bat while playing baseball'. Find frequency of the letter 'h'
[A]: 1


[Q]: Sentence: 'a red bus is stopping at a bus stop'. Find frequency of the letter 's'
[A]:
5