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

[Q]: Sentence: 'a tv in a glass mirror in the bathroom'. Find frequency of the letter 'h'
[A]: 2


[Q]: Sentence: 'a man flying through the air on a bicycle'. Find frequency of the letter 'u'
[A]: 1


[Q]: Sentence: 'a person working behind the counter of a food truck'. Find frequency of the letter 'd'
[A]:
2