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

Sentence: 'a view from a bathroom shows an open door'. Find frequency of the letter 'o'
7

Sentence: 'a man holding a baseball bat an playing baseball'. Find frequency of the letter 'l'
6

Sentence: 'many people stand near a display of vegetables on a stormy day'. Find frequency of the letter 'n'

4