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

[Q]: Sentence: 'a chair and umbrella on a sandy beach'. Find frequency of the letter 's'
[A]: 1


[Q]: Sentence: 'a woman and a child walking down a street with a kite'. Find frequency of the letter 'n'
[A]: 4


[Q]: Sentence: 'a man on a skateboard on the sidewalk'. Find frequency of the letter 'e'
[A]:
3