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

Sentence: 'an old boat on a beach near a large body of water'. Find frequency of the letter 'a'
8

Sentence: 'a person riding a skate board on a city street'. Find frequency of the letter 'a'
5

Sentence: 'a woman in pink swings her tennis racket'. Find frequency of the letter 's'

3