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

[EX Q]: Sentence: 'a softball player holding the bat on first base'. Find frequency of the letter 't'
[EX A]: 4

[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 bear is laying down with its paws over the rocks'. Find frequency of the letter 'r'
[EX A]:
3