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

[Q]: Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'
[A]: 5


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


[Q]: Sentence: 'a bunch of people having a metting in a basketball court'. Find frequency of the letter 'b'
[A]:
3