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: 'flower in a vase full of water sitting on a stand '. Find frequency of the letter 'l'
[A]: 3


[Q]: Sentence: 'a bathroom with bathtub, sink, rug, and toilet'. Find frequency of the letter 'a'
[A]:
4