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

[EX Q]: Sentence: 'a small wrinkley dog wearing a bow tie'. Find frequency of the letter 'e'
[EX A]: 3

[EX Q]: Sentence: 'a herd of giraffe walking across a field'. Find frequency of the letter 'k'
[EX A]: 1

[EX Q]: Sentence: 'a bunch of school buses that are parked in a big lot'. Find frequency of the letter 'a'
[EX A]:
5