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

[Q]: Sentence: 'there is a baseball game on and a few people are watching'. Find frequency of the letter 'i'
[A]: 2


[Q]: Sentence: 'two computers and a laptop set up on a desk'. Find frequency of the letter 'r'
[A]: 1


[Q]: Sentence: 'a man is texting in the middle of a store'. Find frequency of the letter 's'
[A]:
2