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

[Q]: Sentence: 'a white toilet sitting next to a bathroom sink'. Find frequency of the letter 'b'
[A]: 1


[Q]: Sentence: 'a giraffe shares a habitat with a zebra, an ostrich, and an okapi'. Find frequency of the letter 'e'
[A]: 3


[Q]: Sentence: 'two unique sandwiches are sitting on a restaurant bar'. Find frequency of the letter 't'
[A]:
5