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

[Q]: Sentence: 'a big bear walks through some grass'. Find frequency of the letter 'a'
[A]: 4


[Q]: Sentence: 'a person is water skiing and there are birds flying around above them'. Find frequency of the letter 'n'
[A]: 5


[Q]: Sentence: 'a group of young children on a field playing soccer'. Find frequency of the letter 'n'
[A]:
4