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

Sentence: 'this is a sign in front of a large cathedral'. Find frequency of the letter 'a'
5

Sentence: 'a photo of a small boat on a shore'. Find frequency of the letter 'f'
1

Sentence: 'a man riding his skateboard down low as he turns'. Find frequency of the letter 'g'

1