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

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

[EX Q]: Sentence: 'person wearing all white leaned up against a wall with a yellow sign'. Find frequency of the letter 'a'
[EX A]: 8

[EX Q]: Sentence: 'a group of young boys standing around a soccer field kicking around a soccer ball'. Find frequency of the letter 'k'
[EX A]:
2