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

Sentence: 'a small wrinkley dog wearing a bow tie'. Find frequency of the letter 'e'
3

Sentence: 'people playing wii bowling in a modern library'. Find frequency of the letter 'o'
3

Sentence: 'a baby calf has a tag on its right ear'. Find frequency of the letter 'n'

1