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

[EX Q]: Sentence: 'two persons standing outside a moving sub train'. Find frequency of the letter 'a'
[EX A]: 3

[EX Q]: Sentence: 'a black cat laying down on a bed'. Find frequency of the letter 'y'
[EX A]: 1

[EX Q]: Sentence: 'a well browned baguette with a hot dog baked inside'. Find frequency of the letter 'i'
[EX A]:
3