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

[Q]: Sentence: 'a family out snow skiing on a blustery day'. Find frequency of the letter 'i'
[A]: 3

[Q]: Sentence: 'two young ladies that are dancing in the room together'. Find frequency of the letter 'a'
[A]: 4

[Q]: Sentence: 'people at different kitchen stations preparing and serving food'. Find frequency of the letter 's'
[A]:
3