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

[Q]: Sentence: 'a blue tripocal bird is perched on a wooden fence'. Find frequency of the letter 'd'
[A]: 3


[Q]: Sentence: 'a bunch of green bananas is hanging on a tree'. Find frequency of the letter 'n'
[A]: 7


[Q]: Sentence: 'a couple of buildings that has a bus out front'. Find frequency of the letter 'a'
[A]:
4