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

[EX Q]: Sentence: 'two people are riding on canoes down a river'. Find frequency of the letter 'e'
[EX A]: 5

[EX Q]: Sentence: 'a young man riding a skateboard near a forest'. Find frequency of the letter 'd'
[EX A]: 2

[EX Q]: Sentence: 'a brown and white dog in a top hat and bow tie'. Find frequency of the letter 'b'
[EX A]:
2