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 bed with a dog laying on it next to two laptop computers'. Find frequency of the letter 'n'
3

Sentence: 'two teenagers are toward the ocean with surfboards'. Find frequency of the letter 'n'

2