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

[EX Q]: Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'
[EX A]: 7

[EX Q]: Sentence: 'a man in costume talking on a cell phone'. Find frequency of the letter 'm'
[EX A]: 2

[EX Q]: Sentence: 'a man in a cowboy hat throwing a frisbee on a field'. Find frequency of the letter 'c'
[EX A]:
1