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

Sentence: 'a toilet filled with a brown liner and dirty water'. Find frequency of the letter 't'
5

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

Sentence: 'a curly brown dog is laying beside a novel'. Find frequency of the letter 'i'

3