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

Sentence: 'a cat sprawls out and sleeps on its back on a lounge chair with an acorn theme'. Find frequency of the letter 'r'
3

Sentence: 'a bed with a mattress that has nothing on it'. Find frequency of the letter 'a'
5

Sentence: 'an old fashioned kitchen with pink refrigerator and green stove'. Find frequency of the letter 'k'

2