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

Sentence: 'there is no image here to provide a caption for'. Find frequency of the letter 'o'
5

Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'
3

Sentence: 'a grey hummingbird by fence and tree branches'. Find frequency of the letter 'y'
2