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

[Q]: Sentence: 'a dog sitting in the back of a truck flat bed'. Find frequency of the letter 'h'
[A]: 1


[Q]: Sentence: 'a man working on a small laptop on a wooden table'. Find frequency of the letter 'l'
[A]: 4


[Q]: Sentence: 'a picture of a busy street from a bus window'. Find frequency of the letter 's'
[A]:
3