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: 'a few men walking through a market place'. Find frequency of the letter 'f'
1

Sentence: 'this is an image of a woman playing tennis'. Find frequency of the letter 'f'
1