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

Sentence: 'a man with a large grey and black beard and glasses and a tie'. Find frequency of the letter 'e'
5

Sentence: 'a man flying through the air on top of a skateboard'. Find frequency of the letter 'r'
3

Sentence: 'a man surfing a wave in a mountainous area'. Find frequency of the letter 'a'

8