In this task, you need to count the number of times the given letter appears in the given sentence.
--------
Question: Sentence: 'a gray colored pigeon that is perched on a railing outside of a building, with other buildings in the background'. Find frequency of the letter 'e'

Answer: 7

Question: Sentence: 'a double-decker bus covered in children's illustrations driving next to a van'. Find frequency of the letter 'a'

Answer: 4

Question: Sentence: 'three cows in a grass field eating grass'. Find frequency of the letter 'e'

Answer:
4