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

[Q]: Sentence: 'a young girl skiing down a snowy mountain'. Find frequency of the letter 'l'
[A]: 1


[Q]: Sentence: 'a red train traveling down train tracks near a forest'. Find frequency of the letter 'f'
[A]: 1


[Q]: Sentence: 'the old sign with chipped paint has three street names on it'. Find frequency of the letter 't'
[A]:
7