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

Sentence: 'the small black and white dog holds onto a frisbee'. Find frequency of the letter 'h'
3

Sentence: 'two baseball players high five each other during a game'. Find frequency of the letter 'y'
1

Sentence: 'a traffic light pole sitting in an intersection late at night'. Find frequency of the letter 'n'
6