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

Sentence: 'there is a person standing on a blue towel'. Find frequency of the letter 'n'
4

Sentence: 'a woman standing next to a man on a motorcycle in front of a market'. Find frequency of the letter 'l'
1

Sentence: 'various plates sit on a table containing meat, broccoli, and other foods'. Find frequency of the letter 'a'
7