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

Sentence: 'a blue tripocal bird is perched on a wooden fence'. Find frequency of the letter 'd'
3

Sentence: 'a photo of a couple of people at a convention'. Find frequency of the letter 'v'
1

Sentence: 'a man wearing shades is standing next to a stop sign'. Find frequency of the letter 's'

6