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

Sentence: 'a young boy wearing black and holding a skateboard on the sidewalk'. Find frequency of the letter 'n'
5

Sentence: 'a boy swinging a bat while playing baseball'. Find frequency of the letter 'h'
1

Sentence: 'a bus is stopped in front of a graphic statue'. Find frequency of the letter 'e'

2