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

[Q]: Sentence: 'a person does a trick on a ramp on a snowboard'. Find frequency of the letter 's'
[A]: 3


[Q]: Sentence: 'a photo of a small boat on a shore'. Find frequency of the letter 'f'
[A]: 1


[Q]: Sentence: 'a man sitting inside a green military truck talking to someone'. Find frequency of the letter 'i'
[A]:
7