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

[EX Q]: Sentence: 'a man in his car eating a donut'. Find frequency of the letter 'm'
[EX A]: 1

[EX Q]: Sentence: 'a construction sign is displayed on a street'. Find frequency of the letter 'i'
[EX A]: 4

[EX Q]: Sentence: 'a couple of boats are sitting in the water'. Find frequency of the letter 'a'
[EX A]:
4