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: 'a person that is looking out his window'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'a cook hands over a plate full of barbecued food to another man'. Find frequency of the letter 'f'
[A]:
3