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

[EX Q]: Sentence: 'a young boy holding a piece of paper on top of a table'. Find frequency of the letter 'y'
[EX A]: 2

[EX Q]: Sentence: 'there is a woman pointing at something with her dog'. Find frequency of the letter 'i'
[EX A]: 5

[EX Q]: Sentence: 'several bicycles are parked next to the window of a brown brick building that has flower boxes on the window'. Find frequency of the letter 'n'
[EX A]:
6