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

Sentence: 'a person that is looking out his window'. Find frequency of the letter 'n'
3

Sentence: 'a giraffe shares a habitat with a zebra, an ostrich, and an okapi'. Find frequency of the letter 'e'
3

Sentence: 'a photo of an electric piano next to a window and a chair'. Find frequency of the letter 'h'

2