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

Sentence: 'a man sitting inside a green military truck talking to someone'. Find frequency of the letter 'i'
7

Sentence: 'a man in costume talking on a cell phone'. Find frequency of the letter 'm'
2

Sentence: 'a  young woman sitting near a tree eating food'. Find frequency of the letter 'n'

5