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: 'cars parked outside if a retail store'. Find frequency of the letter 'd'
[EX A]: 2

[EX Q]: Sentence: 'a close up view of a small zebra in the grass'. Find frequency of the letter 'w'
[EX A]:
1