In this task, you need to count the number of times the given letter appears in the given sentence.
--------
Question: Sentence: 'the receipts from a meal at a restaurant are for a sandwich, chili, and apple'. Find frequency of the letter 'u'

Answer: 1

Question: Sentence: 'a person is water skiing and there are birds flying around above them'. Find frequency of the letter 'n'

Answer: 5

Question: Sentence: 'this is a desk with a computer on it'. Find frequency of the letter 's'

Answer:
3