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

[Q]: Sentence: 'red chair next to side table with lamp in residential home'. Find frequency of the letter 'm'
[A]: 2

[Q]: Sentence: 'a man is water skiing on a river'. Find frequency of the letter 'r'
[A]: 3

[Q]: Sentence: 'a person sitting at a desk with a cat in front of a keyboard'. Find frequency of the letter 'i'
[A]:
4