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: 'some giraffes moving across a big grass field'. Find frequency of the letter 'e'
3

Sentence: 'older man preparing to blow out a set of candles'. Find frequency of the letter 't'
3