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

Sentence: 'a person standing operating a cell phone in a room'. Find frequency of the letter 'n'
6

Sentence: 'an airplane is being towed away from the jet bridge'. Find frequency of the letter 's'
1

Sentence: 'a cat stands with its front paws on a suitcase'. Find frequency of the letter 's'

6