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

[EX Q]: Sentence: 'a group of giraffes walk together by a hill'. Find frequency of the letter 'b'
[EX A]: 1

[EX Q]: Sentence: 'an commercial airline airplane flies above the clouds'. Find frequency of the letter 'n'
[EX A]: 3

[EX Q]: Sentence: 'two pizzas on a table being served at a restaurant'. Find frequency of the letter 'r'
[EX A]:
3