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

Sentence: 'a toasted sub sandwich is next to a salad'. Find frequency of the letter 'a'
6

Sentence: 'apples, pears, and oranges are piled up for sale'. Find frequency of the letter 'a'
6

Sentence: 'the motorcycle is cleaned and polished and ready to be rode'. Find frequency of the letter 'a'

4