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

[EX Q]: Sentence: 'some giraffes moving across a big grass field'. Find frequency of the letter 'e'
[EX A]: 3

[EX Q]: Sentence: 'a young girl skiing down a snowy mountain'. Find frequency of the letter 'l'
[EX A]: 1

[EX Q]: Sentence: 'a man opening up a package sitting on a couch'. Find frequency of the letter 'n'
[EX A]:
5