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

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

[EX Q]: Sentence: 'a baseball player dropping his bat and starting to run'. Find frequency of the letter 'o'
[EX A]: 2

[EX Q]: Sentence: 'a young man riding skis through a snow covered forest'. Find frequency of the letter 'r'
[EX A]:
4