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

[EX Q]: Sentence: 'three people are gathered around sitting on a park bench'. Find frequency of the letter 'g'
[EX A]: 2

[EX Q]: Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'
[EX A]: 4

[EX Q]: Sentence: 'a laptop computer sitting on top of a desk next to a monitor and keyboard'. Find frequency of the letter 'f'
[EX A]:
1