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

[EX Q]: Sentence: 'a couple of men sitting next to each other under an umbrella'. Find frequency of the letter 'n'
[EX A]: 5

[EX Q]: Sentence: 'three birds are sitting on a tree in a forest'. Find frequency of the letter 'h'
[EX A]: 1

[EX Q]: Sentence: 'a number of animals with in a field with trees near by'. Find frequency of the letter 'e'
[EX A]:
5