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

Sentence: 'two men sitting quietly on a park bench'. Find frequency of the letter 'a'
2

Sentence: 'an elephant has taken a man's hat in its trunk'. Find frequency of the letter 'p'
1

Sentence: 'the people in the truck are riding in the parade'. Find frequency of the letter 'e'
7