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

Sentence: 'three young people goofing around; one of the guys has a football, the girl has a teddy bear'. Find frequency of the letter 'd'
3

Sentence: 'a black animal in dirt area below trees and rocks'. Find frequency of the letter 'n'
3

Sentence: 'a man sitting next to a brown cow on a bench'. Find frequency of the letter 's'

1