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

Sentence: 'a tall building with antenna stands before a jet flying in the background'. Find frequency of the letter 't'
6

Sentence: 'a number of small boats on a beach near an umbrella'. Find frequency of the letter 's'
2

Sentence: 'a couple of people on bikes ride through the street'. Find frequency of the letter 'o'
5