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

[Q]: Sentence: 'an old glass vase containing flowers on a glass table'. Find frequency of the letter 'b'
[A]: 1


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


[Q]: Sentence: 'a baseball player on the feild with a bat'. Find frequency of the letter 'b'
[A]:
3