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

[EX Q]: Sentence: 'a man flying through the air on a bicycle'. Find frequency of the letter 'u'
[EX A]: 1

[EX Q]: Sentence: 'two elephants walking on cement next to wall'. Find frequency of the letter 'n'
[EX A]: 5

[EX Q]: Sentence: 'the head of a giraffe with trees behind it'. Find frequency of the letter 'f'
[EX A]:
3