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

[EX Q]: Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'
[EX A]: 10

[EX Q]: Sentence: 'a photo of a toilet which is not clean'. Find frequency of the letter 'w'
[EX A]: 1

[EX Q]: Sentence: 'a kitchen counter next to a stove and oven'. Find frequency of the letter 'n'
[EX A]:
5