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

Sentence: 'a couple of people are sitting at a table'. Find frequency of the letter 'e'
5

Sentence: 'the receipts from a meal at a restaurant are for  a sandwich, chili, and apple'. Find frequency of the letter 'u'
1

Sentence: 'a cow walks on boats in a field'. Find frequency of the letter 'w'

2