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

[Q]: Sentence: 'a group of people stand inside of a big room'. Find frequency of the letter 'o'
[A]: 6


[Q]: Sentence: 'a tennis player after hitting a shot back to the other side of the court'. Find frequency of the letter 'n'
[A]: 3


[Q]: Sentence: 'a lot people walking in the rain, holding umbrellas'. Find frequency of the letter 'g'
[A]:
2