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

Sentence: 'a man sitting in front of a laptop computer next to a child'. Find frequency of the letter 'e'
2

Sentence: 'a man riding on the back of a white horse next to other horses'. Find frequency of the letter 'o'
6

Sentence: 'small dirt road on a hill beside a small city'. Find frequency of the letter 's'

3