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

[Q]: Sentence: 'a stuffed animal sitting on an empty bed'. Find frequency of the letter 'u'
[A]: 1


[Q]: Sentence: 'two men sitting quietly on a park bench'. Find frequency of the letter 'a'
[A]: 2


[Q]: Sentence: 'a large bathtub sits in front of two sinks'. Find frequency of the letter 'o'
[A]:
3