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

[Q]: Sentence: 'there is a woman pointing at something with her dog'. Find frequency of the letter 'i'
[A]: 5


[Q]: Sentence: 'man sitting on the side of a van playing the guitar'. Find frequency of the letter 'm'
[A]: 1


[Q]: Sentence: 'a black dog with a red collar standing in a kitchen'. Find frequency of the letter 'k'
[A]:
2