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

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

[EX Q]: Sentence: 'the small black and white dog holds onto a frisbee'. Find frequency of the letter 'h'
[EX A]: 3

[EX Q]: Sentence: 'three sinks and a mirror in a public restroom'. Find frequency of the letter 'a'
[EX A]:
3